code for eternity !!!

LINQ ElementAt and ElementAtOrDefault

raj — Wed, 13 Aug 2008 14:02:00 GMT

We can use the ElementAt extension method of LINQ to return the element at a specified index (zero based) in a sequence. However the ElementAt extension method would throw the System.ArguementOutOfRangeException when the specified index is a negative value or not less than the size of the sequence. In such a scenario, we can use the ElementAtOrDefault extenion method which would return the default value of a type instead of throwing the System.ArguementOutOfRangeException.

Code example (both in C# and VB.NET) with comments below:

C#:

// Create a new generic list of ints
List<int> l = new List<int>();

    l.Add(1); // Add 1 to the list
    l.Add(5); // Add 5 to the list
    l.Add(3); // Add 3 to the list

// Returns 1 as 1 exists at index 0
int value = l.ElementAt(0);

// Returns 3 as 3 exists at index 2
value = l.ElementAt(2);

    // Returns the default value of int which is 0
    // since no element in the list exists at index 3
    value = l.ElementAtOrDefault(3);

    // Throws System.ArguementOutOfRangeException
    // since no element in the list exists at index 3
    value = l.ElementAt(3);

VB.NET:

' Create a new generic list of ints
Dim l As New List(Of Integer)

    l.Add(1) ' Add 1 to the list
    l.Add(5) ' Add 5 to the list
    l.Add(3) ' Add 3 to the list

' Returns 1 as 1 exists at index 0
Dim value As Integer = l.ElementAt(0)

' Returns 3 as 3 exists at index 2
value = l.ElementAt(2)

    ' Returns the default value of int which is 0
    ' since no element in the list exists at index 3
    value = l.ElementAtOrDefault(3)

    ' Throws System.ArguementOutOfRangeException
    ' since no element in the list exists at index 3
    value = l.ElementAt(3)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

T-SQL Function to Get Int From Varchar

raj — Tue, 20 May 2008 10:48:00 GMT

I recently had to write a T-SQL function which cleans up all non numeric characters from a varchar variable and returns the int value of the remaining numeric characters. If no numeric characters exist, the function should return zero. I thought it would be nice to share this with you and I hope you find this useful ;-) Here is the function:

    CREATE FUNCTION [dbo].[GetIntFromVarchar]
    (
        @originalString varchar(50)
    )

RETURNS int

BEGIN

        -- declare local variable to hold numeric characters
        -- and assign default value of empty string
        DECLARE @retVal varchar(50)
        SET @retVal = ''

        -- declare local variable to loop through @originalString
        -- and assign initial value of 1
        DECLARE @loop int
        SET @loop = 1

-- loop through every character in @originalString
WHILE @loop <= LEN(@originalString)

            BEGIN

                IF ISNUMERIC(SUBSTRING(@originalString, @loop, 1)) = 1

                    BEGIN

                        -- if numeric character found, append it to @retVal
                        SET @retVal = @retVal + SUBSTRING(@originalString, @loop, 1)

END

SET @loop = @loop + 1 -- increment value of @loop by 1

            END

        -- set @retVal to '0' if no numeric characters found
        IF @retVal = ''

BEGIN

SET @retVal = '0'

            END

        -- return int value of numeric characters found
        -- by casting @retVal to int
        RETURN CAST(@retVal as int)

END

Once you have created this function, execute below T-SQL statements to verify the same:

    PRINT dbo.GetIntFromVarchar('R1A2J3') -- returns 123
    PRINT dbo.GetIntFromVarchar('COOL456CODER') -- returns 456
    PRINT dbo.GetIntFromVarchar('789') -- returns 789
    PRINT dbo.GetIntFromVarchar('GEEK') -- returns 0

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Developers are Born Brave

raj — Fri, 16 May 2008 16:15:00 GMT

Reality about software development. Below image says it all ;-) Cheers to every coder reading this blog post :-) Please scroll to the right if you cannot see the entire image at 1 glance or click here to view / download the image in a seperate window.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Coders versus Project Managers

raj — Wed, 14 May 2008 10:15:00 GMT

Few months back, I got below joke emailed to me by my friend who is also a passionate coder. In my personal (and humble) opinion, below joke hits jackpot with the current state of 9 out of 10 IT companies in India, which are headed by people who have zero or very little technical background. And perhaps this explains why Indian IT companies still have to market themselves as low cost outsourcing destinations to win business any why we still dont have too many Product based IT companies in India :-) Is the story same in your country too? Let me know, I would love to hear :-)

Here is the joke, enjoy and forward this to all your coder friends ;-)

A woman in a hot air balloon realized she was lost.

She reduced altitude and spotted a man below. She descended a bit more and shouted, "Excuse me, can you help me? I promised a friend I would meet him an hour ago but I don't know where I am."

The man below replied, "You're in a hot air balloon hovering approximately 30 feet above the ground. You're between 40 and 41 degrees north latitude and between 59 and 60 degrees west longitude."

"You must be an engineer" said the balloonist.

"I am", replied the man. "How did you know?"

"Well", answered the balloonist, "everything you told me is technically correct, but I've no idea what to make of your information, and the fact is I'm still lost. Frankly, you've not been much help at all. If anything you've delayed my trip even more."

The man below responded, "You must be in management."

"I am," replied the balloonist, "but how did you know?"

"Well", said the man, "You don't know where you are or where you're going. You have risen to where you are due to a large quantity of hot air. You made a promise which you've no idea how to keep, and you expect people beneath you to solve your problems"

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

LINQ Single and SingleOrDefault

raj — Sat, 10 May 2008 13:27:00 GMT

We can use the Single extension method of LINQ to return the only element in a sequence that satisfies a specified condition. However the Single extension method would throw the System.InvalidOperationException when no element in a sequence satisfies a specified condition. In such a scenario, we can use the SingleOrDefault extenion method which would return the default value of a type instead of throwing the System.InvalidOperationException.

Also, both Single as well as SingleOrDefault extension methods would throw the System.InvalidOperationException when more than one element in a sequence satisfy a specified condition. We can use First or Last extensions methods of LINQ in such scenarios.

Code example (both in C# and VB.NET) with comments below:

C#:

// Create a new generic list of ints
List<int> l = new List<int>();

    l.Add(1); // Add 1 to the list
    l.Add(5); // Add 5 to the list
    l.Add(3); // Add 3 to the list

// Returns 1 as only 1 satisfies the condition
int value = l.Single(i => i == 1);

    // Returns the default value of int which is 0
    // since no element in the list equals 4
    value = l.SingleOrDefault(i => i == 4);

    // Throws System.InvalidOperationException
    // since no element in the list equals 4
    value = l.Single(i => i == 4);

    // Throws System.InvalidOperationException
    // since both 5 and 3 are greater than 1
    value = l.Single(i => i > 1);
    value = l.SingleOrDefault(i => i > 1);

VB.NET:

' Create a new generic list of ints
Dim l As New List(Of Integer)

    l.Add(1) ' Add 1 to the list
    l.Add(5) ' Add 5 to the list
    l.Add(3) ' Add 3 to the list

' Returns 1 as only 1 satisfies the condition
Dim value As Integer = l.Single(Function(i) i = 1)

    ' Returns the default value of int which is 0
    ' since no element in the list equals 4
    value = l.SingleOrDefault(Function(i) i = 4)

    ' Throws System.InvalidOperationException
    ' since no element in the list equals 4
    value = l.Single(Function(i) i = 4)

    ' Throws System.InvalidOperationException
    ' since both 5 and 3 are greater than 1
    value = l.Single(Function(i) i > 1)
    value = l.SingleOrDefault(Function(i) i > 1)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

AddItem Extension Method for BulletedList, CheckBoxList, DropDownList, ListBox, RadioButtonList

raj — Fri, 09 May 2008 15:03:00 GMT

We would have to write the below code to add a new item (with value) to any of these 5 controls (BulletedList, CheckBoxList, DropDownList, ListBox, RadioButtonList)

C#:

    bulletedList.Items.Add(new ListItem("text", "value"));
    checkBoxList.Items.Add(new ListItem("text", "value"));
    dropDownList.Items.Add(new ListItem("text", "value"));
    listBox.Items.Add(new ListItem("text", "value"));
    radioButtonList.Items.Add(new ListItem("text", "value"));

VB:

    bulletedList.Items.Add(New ListItem("text", "value"))
    checkBoxList.Items.Add(New ListItem("text", "value"))
    dropDownList.Items.Add(New ListItem("text", "value"))
    listBox.Items.Add(New ListItem("text", "value"))
    radioButtonList.Items.Add(New ListItem("text", "value"))

I find it quite painful to write so much code just to add a new item (with value) to these controls and so I created a new AddItem extension method for the ListControl class (since all these 5 controls inherit from the ListControl class)

C#:

    public static void AddItem(this ListControl lc, string text, string value)
    {
        lc.Items.Add(new ListItem(text, value));
    }

VB:

    <Extension()> _
    Public Sub AddItem(ByVal lc As ListControl, ByVal text As String, ByVal value As String)
        lc.Items.Add(New ListItem(text, value))
    End Sub

Now I can simply write the above code in a much simpler and cleaner way like below:

C#:

    bulletedList.AddItem("text", "value");
    checkBoxList.AddItem("text", "value");
    dropDownList.AddItem("text", "value");
    listBox.AddItem("text", "value");
    radioButtonList.AddItem("text", "value");

VB:

    bulletedList.AddItem("text", "value")
    checkBoxList.AddItem("text", "value")
    dropDownList.AddItem("text", "value")
    listBox.AddItem("text", "value")
    radioButtonList.AddItem("text", "value")

Just 1 extension method which works for 5 controls to solve the problem :-) Cheers to object inheritance and cheers to Extension Methods ;-)

Note: You can find a list of other cool and useful Extension Methods coded by me here

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Using Initial Capacity Constructor of StringBuilder for Extreme Performace

raj — Thu, 08 May 2008 12:13:00 GMT

You must have come across plenty of articles on the internet which talk about using the StringBuilder class when computing large strings for performance gains. Nothing wrong with that. However I have not seen many coders using the Initial Capacity constructor of the StringBuilder class which can further improve performace.

Lets take a real world example. Suppose we had to compute a csv (comma seperated values) file for a table named Users which had the following structure:

UserID int
FirstName nvarchar(20)
LastName nvarchar(20)

Our csv file would look like (for 2 records):

1,Paul,Graham
2,Scott,Guthrie

Most coders would write the below code to compute the csv file:

// Populate Users DataTable
DataTable dtUsers = SomeFunctionWhichReturnsUsersDataTable();

// Declare new StringBuilder
System.Text.StringBuilder sb = new System.Text.StringBuilder();

    // Loop through Users DataTable
    for (int j = 0; j < dtUsers.Rows.Count; j++)
    {
        sb.Append(dtUsers.Rows[j]["UserID"].ToString()); // Append UserID
        sb.Append(","); // Append comma
        sb.Append(dtUsers.Rows[j]["FirstName"].ToString()); // Append FirstName
        sb.Append(","); // Append comma
        sb.Append(dtUsers.Rows[j]["LastName"].ToString()); // Append LastName
        sb.AppendLine(); // Append new line
    }

return sb.ToString(); // Return StringBuilder contents

Now lets write the above code more intelligently by using the Initial Capacity constructor of the StringBuilder class. We can actually guess the approximate length of the csv file before hand by considering below points:

Max length of UserID can be 10 characters, since max value of UserID can be 2147483647, since its datatype is int
Max length of FirstName can be 20 characters, since its datatype is nvarchar(20)
Max length of LastName can be 20 characters, since its datatype is nvarchar(20)
Also each csv file record has 2 comma characters which act as seperators, and 1 new line character

Therefore the max length per record can be 54 characters (10[UserID] + 20[FirstName] + 20[LastName] + 2[2 comma characters] + 2[1 new line character]). So now we are absolutely sure that our csv file would have a max length of (54 * Number of Records) characters.

If you are hell bent on having just one and only one memory allocation for the StringBuilder class, go ahead and set the Initial Capacity of the StringBuilder class to (54 * Number of Rows). However doing this would more often than not result in a lot of memory wastage as not all records would have their UserID set to 10 digit integers or their FirstName and LastName set to 20 character long strings. Therefore I usually follow the divide by 2 rule where I divide the max length per record value by 2. This way I am sure there wont ever be more than 2 memory (re)allocations and more often than not just a single memory allocation would do the job. Below is the intelligent version of above code:

// Populate Users DataTable
DataTable dtUsers = SomeFunctionWhichReturnsUsersDataTable();

// Set a value of 54 to maxLengthPerRecord
int maxLengthPerRecord = 54;

// Apply divide by 2 rule
maxLengthPerRecord = maxLengthPerRecord / 2;

    // Compute initialCapacity value
    int initialCapacity = dtUsers.Rows.Count * maxLengthPerRecord;

    // Declare new StringBuilder using the Initial Capacity constructor
    System.Text.StringBuilder sb = new System.Text.StringBuilder(initialCapacity);

You might be thinking this is too much of an effort to save on a few memory reallocations. But the geek in me tries to visualize the performance gains and number of memory reallocations (read garbage collection cycles which are so expensive) which can be saved if we had to do the same task for a table with many columns and tens of thousands of records :-)

Note: You can also consider dividing the max length per record by 3 or even 4, it all depends on your data structures and data patterns. Also the above code example uses a DataTable. However you can apply the same logic on a generic list or a DataReader as well.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

T-SQL Query to Find the Second Lowest Column Value in a Table

raj — Wed, 30 Apr 2008 08:41:00 GMT

After reading my earlier post T-SQL Query to Find the Second Highest Column Value in a Table a lot of users asked me to also help them with writing a query to find the second lowest column value in a table. So here it is: If we had a table named Employee which had a column named Salary and we had to find the second lowest Salary in the Employee table, the query for the same would be:

SELECT TOP 1 Salary FROM (SELECT TOP 2 Salary FROM Employee ORDER BY Salary ASC) AS E ORDER BY Salary DESC

If we ran the above query against the Employee table which had the following 5 rows:

5000
4000
3000
2000
1000

The subquery or the inner query would return the top 2 rows in ascending Salary order which would be:

1000
2000

The outer query would then select the top 1 row from the subquery results in descending Salary order which would be:

2000

Note that if we had to get the fourth lowest Salary, we could do so by simply changing the subquery from TOP 2 to TOP 4

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

LINQ Last and LastOrDefault

raj — Sun, 27 Apr 2008 08:31:00 GMT

We can use the Last extension method of LINQ to return the last element in a sequence that satisfies a specified condition. However the Last extension method would throw the System.InvalidOperationException when no element in a sequence satisfies a specified condition. In such a scenario, we can use the LastOrDefault extenion method which would return the default value of a type instead of throwing the System.InvalidOperationException.

Code example (both in C# and VB.NET) with comments below:

C#:

// Create a new generic list of ints
List<int> l = new List<int>();

    l.Add(1); // Add 1 to the list
    l.Add(5); // Add 5 to the list
    l.Add(3); // Add 3 to the list

// Returns 1 as only 1 satisfies the condition
int value = l.Last(i => i == 1);

    // Returns 3 although both 5 and 3 are greater than 1
    // since 3 appears last in the list
    value = l.Last(i => i > 1);

    // Returns the default value of int which is 0
    // since no element in the list equals 4
    value = l.LastOrDefault(i => i == 4);

    // Throws System.InvalidOperationException
    // since no element in the list equals 4
    value = l.Last(i => i == 4);

VB.NET:

' Create a new generic list of ints
Dim l As New List(Of Integer)

    l.Add(1) ' Add 1 to the list
    l.Add(5) ' Add 5 to the list
    l.Add(3) ' Add 3 to the list

' Returns 1 as only 1 satisfies the condition
Dim value As Integer = l.Last(Function(i) i = 1)

    ' Returns 3 although both 5 and 3 are greater than 1
    ' since 3 appears last in the list
    value = l.Last(Function(i) i > 1)

    ' Returns the default value of int which is 0
    ' since no element in the list equals 4
    value = l.LastOrDefault(Function(i) i = 4)

    ' Throws System.InvalidOperationException
    ' since no element in the list equals 4
    value = l.Last(Function(i) i = 4)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

LINQ First and FirstOrDefault

raj — Fri, 25 Apr 2008 17:22:00 GMT

We can use the First extension method of LINQ to return the first element in a sequence that satisfies a specified condition. However the First extension method would throw the System.InvalidOperationException when no element in a sequence satisfies a specified condition. In such a scenario, we can use the FirstOrDefault extenion method which would return the default value of a type instead of throwing the System.InvalidOperationException.

Code example (both in C# and VB.NET) with comments below:

C#:

// Create a new generic list of ints
List<int> l = new List<int>();

    l.Add(1); // Add 1 to the list
    l.Add(5); // Add 5 to the list
    l.Add(3); // Add 3 to the list

// Returns 1 as only 1 satisfies the condition
int value = l.First(i => i == 1);

    // Returns 5 although both 5 and 3 are greater than 1
    // since 5 appears first in the list
    value = l.First(i => i > 1);

    // Returns the default value of int which is 0
    // since no element in the list equals 4
    value = l.FirstOrDefault(i => i == 4);

    // Throws System.InvalidOperationException
    // since no element in the list equals 4
    value = l.First(i => i == 4);

VB.NET:

' Create a new generic list of ints
Dim l As New List(Of Integer)

    l.Add(1) ' Add 1 to the list
    l.Add(5) ' Add 5 to the list
    l.Add(3) ' Add 3 to the list

' Returns 1 as only 1 satisfies the condition
Dim value As Integer = l.First(Function(i) i = 1)

    ' Returns 5 although both 5 and 3 are greater than 1
    ' since 5 appears first in the list
    value = l.First(Function(i) i > 1)

    ' Returns the default value of int which is 0
    ' since no element in the list equals 4
    value = l.FirstOrDefault(Function(i) i = 4)

    ' Throws System.InvalidOperationException
    ' since no element in the list equals 4
    value = l.First(Function(i) i = 4)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Blackle - Energy Saving Search

raj — Thu, 24 Apr 2008 19:45:00 GMT

Google is the second brain for many coders hungry for information. I as a coder cannot imagine a single day at work without Google. Few days back (22 April to be precise), it was Earth's day and I was wondering how we as coders can do our bit for our planet and fight against Global Warming. So I thought I would blog about Blackle :-)

The idea behind Blackle: Google uses white background which consumes more power, and considering the huge number of queries Google gets (about 200 million each day), according to calculations, a black version of Google would save 750 mega watts / hour per year.

So next time you want to search for information, try http://www.blackle.com :-) For more info on Blackle, visit http://www.blackle.com/about

Also help spread the word about Blackle by telling your coder friends about it, ask them to blog about Blackle incase they have a blog ;-)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Cool Extension Methods for IDataReader Interface

raj — Tue, 15 Apr 2008 22:34:00 GMT

I find it really annoying to use the GetOrdinal method of the DataReader class everytime I have to access data in a strongly typed manner using any of the Get[DataType] methods of the DataReader class. Have a look at below code:

    int employeeID = dr.GetInt32(dr.GetOrdinal("EmployeeID"));
    string firstName = dr.GetString(dr.GetOrdinal("FirstName"));
    bool enabled = dr.GetBoolean(dr.GetOrdinal("Enabled"));

It would be so cool if I could directly specify the table column names like below:

    int employeeID = dr.GetInt32("EmployeeID");
    string firstName = dr.GetString("FirstName");
    bool enabled = dr.GetBoolean("Enabled");

This would save me so much typing and make my code look so much cleaner. The power of Extension Methods make this possible :-) I created a new class named IDataReaderHelper which has 18 Extension Methods in all. You can simply pass the table column names instead of table column indexes to all these 18 Extension Methods, and these 18 Extension Methods would take care of the rest by calling the GetOrdinal method of the DataReader class internally :-). Have a look at the screen shot below:

Note: For readability purpose, above screen shot just highlights 3 of the 18 Extension Methods present in the IDataReaderHelper class. The 18 Extension Methods present in the IDataReaderHelper class are:

GetBoolean
GetByte
GetBytes
GetChar
GetChars
GetData
GetDataTypeName
GetDateTime
GetDecimal
GetDouble
GetFieldType
GetFloat
GetGuid
GetInt16
GetInt32
GetInt64
GetString
GetValue

You can find the entire source code for the IDataReaderHelper class as an attachment with this post available for download. To see all my posts on Extension Methods click here.

Update: Guys please dont forget to check out the Chris's comments (2nd from top) regarding performance issues when using the GetOrdinal method of the DataReader class inside a loop. Thanks for your excellent feedback Chris :-)

Update: Guys please dont forget to check out programatik's post here where he / she has compared performance (using GetOrdinal versus using int inside a loop). His / her post is in Portuguese so you can go to http://www.google.com/translate_t and translate programatik's post from Portuguese to English. It took me 30 minutes to figure out the language of this post ;-) Great work programatik ;-)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

System.Data.DataSetExtensions Assembly Error in Visual Studio 2008 RTM

raj — Sat, 05 Apr 2008 13:27:00 GMT

After upgrading from Visual Studio 2008 Beta 2 to Visual Studio 2008 RTM, I got the following error when I tried to build my ASP.NET 3.5 project which was initially coded using Visual Studio 2008 Beta 2:

Could not load file or assembly 'System.Data.DataSetExtensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.

This error occurs because with Visual Studio 2008 RTM, a newer version (3.5) of the System.Data.DataSetExtensions assembly is available and the older version (2.0) of the System.Data.DataSetExtensions assembly no longer exists.

To resolve this error, simply change your web.config file from:

to:

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Tip/Trick: Making Non Themeable Properties of ASP.NET Controls Themeable

raj — Sat, 29 Mar 2008 13:56:00 GMT

If you have been using ASP.NET themes feature in your ASP.NET projects, you surely must have come across situations where you wished you could set certain properties of controls via skins. For example, in all my ASP.NET projects, I always want to set the Display property of any validator control to Dynamic. Also, I simply hate the idea of setting the ValidationExpression property for every instance of the RegularExpressionValidator control I use in aspx / ascx files where I have to validate an email address. When I tried to set these two properties of the RegularExpressionValidator control via skin, I got the following errors:

The 'Display' property of a control type System.Web.UI.WebControls.RegularExpressionValidator cannot be applied through a control skin.
The 'ValidationExpression' property of a control type System.Web.UI.WebControls.RegularExpressionValidator cannot be applied through a control skin.

This happens because the Display as well as the ValidationExpression properties of the RegularExpressionValidator control are not marked as Themeable. To overcome this, I found a really cool and simple solution (object inheritance to the rescue !!!). I created a new class called NewRegularExpressionValidator which inherits from the RegularExpressionValidator class, and provides a new implementation of these two properties by marking them as Themeable. I created this new class in a new class library project (named ClassLibrary1) and also added the System.Web reference to this class library project. Below is the code for the NewRegularExpressionValidator class:

Next I added a reference to ClassLibrary1 project from my ASP.NET project and defined two skins (Default skin and Email skin) for the NewRegularExpressionValidator control. Have a look at the skin definitions below:

Now I no longer have to explicitly set the Display and ValidationExpression property of each and every RegularExpressionValidator control which validates an email address. Instead, I can simply set their SkinID as Email ;-). See below screen shot on how to use the Email skin in aspx / ascx files:

This also makes it super easy for me to change the ValidationExpression property for a particular type of validation if need be. For example, if a new business rule disallows all hotmail email addresses, I can simply change the ValidationExpression property in the Email skin instead of changing it in multiple aspx / ascx files where I am validating email addresses ;-)

Also note that the Default skin makes sure that every instance of the NewRegularExpressionValidator control in my ASP.NET project (which does not specify a particular SkinID) will have its Display property automatically set to Dynamic ;-)

Note: You can use the same above trick with many other controls to make their Non Themeable properties Themeable. One good example (which I have been using since years) is to make the MaxLength property of a TextBox control Themeable. I find it quite useful to set the MaxLength property of a TextBox through a skin for common inputs which are required in multiple pages of a website (like Email, Password, etc).

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Cool TrimText Extension Method for TextBox

raj — Mon, 03 Mar 2008 08:01:00 GMT

Extension Methods are one of the most powerful features of .NET 3.5 and they can add a lot of flexibility to your code and help in cutting down your code size significantly if used wisely. I have been using a lot of Extension Methods in my code lately. One of them is the TrimText Extension Method for TextBox. While taking user input on any webform or winform (for example when users enter their First Name / Last Name), often, users accidentally add an extra space in the end. If you are a good coder, you would handle such common user mistakes by making sure to trim these input values before adding them to the database. Prior to .NET 3.5, we would have to write the below code to trim the TextBox text:

C#:

TextBox1.Text = TextBox1.Text.Trim();

VB:

TextBox1.Text = TextBox1.Text.Trim()

Now lets see how Extension Methods can help cut down the size of our above code. We create a simple TrimText Extension Method in a static class (C#) or module (VB) like below:

C#:

public static class ExtensionMethods
{

    public static void TrimText(this TextBox t)
    {
       t.Text = t.Text.Trim();
    }

}

VB:

Imports System.Runtime.CompilerServices

Public Module ExtensionMethods

    <Extension()> _
    Public Sub TrimText(ByVal t As TextBox)
        t.Text = t.Text.Trim()
    End Sub

End Module

Once we have our TrimText Extension Method in place, we can achieve the same task by simply calling the TrimText Extension Method from any TextBox object:

C#:

TextBox1.TrimText();

VB:

TextBox1.TrimText()

Notice how we have cut down the code and the code looks so much neater now ;-) I will post a few more examples of useful Extension Methods which I am using over the coming weeks. For those new to .NET 3.5, click here to know more about Extension Methods.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Creating Self Signed SSL Certificates on IIS 6.0 and Windows Server 2003

raj — Fri, 15 Feb 2008 08:48:00 GMT

If you need to deploy and test your code in SSL environment on IIS 6.0 and Windows Server 2003, but you do not have a valid SSL certificate on your development / test server issued by a trusted third party Certificate Authority (since it costs money), you can easily do so by creating a self signed test certificate using a tool called SelfSSL which comes with IIS 6.0 Resource Kit Tools. SelfSSL is a console line application which is free to use :-). You can download IIS 6.0 Resource Kit Tools from here.

After downloading and executing this kit, make sure you either choose Complete installation option or if you choose Custom installation option, make sure you have selected the SelfSSL feature. See below step by step screen shots for the Custom installation option.

Step 1: Click Next.

Step 2: Choose I Agree and click Next.

Step 3: Enter appropriate details and click Next.

Step 4: Choose Custom installation option if you just want to install SelfSSL else choose Complete installation option to install all features and click Next.

Step 5: Enter the installation location and click Next.

Step 6: Select SelfSSL and click Next.

Step 7: Review settings and click Next.

Step 8: Click Finish.

Once you have successfully installed, click on Start > All Programs > IIS Resources > SelfSSL > SelfSSL to run the SelfSSL utility. On doing so, you should see the command prompt along with help instructions (see below screen shot).

If you simply type selfssl.exe and press enter, it would use the default settings to install the SSL certificate which are equivalent to:

/N:CN=<YOUR COMPUTER NAME> (common name of the certificate)
/K:1024 (key length of the certificate)
/V:7 (validity of the certificate in days)
/S:1 (ID of the site to which the certificate needs to be installed)
/P:443 (SSL port)

Type selfssl.exe and press enter, then type y and press enter again to confirm the installation (see screen shot below).

The most important option here is the site id parameter and SelfSSL uses the site id 1 by default which maps to "Default Web Site".

To find the site id for any website in IIS 6.0 you can simply execute iisweb.vbs /query "<NAME OF THE WEBSITE>" from command prompt (see below screen shot).

In the above screen shot, you can clearly see that I executed iisweb.vbs /query "Default Web Site" to find the site id for "Default Web Site" which is "W3SVC/1", however we are only interested in the text which follows "W3SVC/" which is "1".

Suppose you had another website by the name "RajTest" and you wanted to install a test SSL certificate having common name "RajTestCertificate" valid for 10 days to "RajTest" on port 444, you would first find the site id for "RajTest" by executing the following command at command prompt: iisweb.vbs /query "RajTest". Once you know the site id for "RajTest" (lets assume it was "1234567") you would execute the following command at the SelfSSL command prompt: selfssl.exe /N:CN=RajTestCertificate /V:10 / S:1234567 /P:444

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Building a Web 2.0 Portal with ASP.NET 3.5

raj — Wed, 13 Feb 2008 15:40:00 GMT

I recently purchased this great new book named Building a Web 2.0 Portal with ASP.NET 3.5 by Omar Al Zabir and I would highly recommend this book to any architect or developer who is interested in learning how to design and develop world class highly scalable ASP.NET web portals using the latest and coolest Microsoft.NET technologies like ASP.NET 3.5, LINQ, Windows Workflow Foundation (WWF), ASP.NET AJAX, etc.

To me, this is one of the best books ever written on ASP.NET because unlike most other books, this book deals with real world problems which architects and developers face with heavy duty ASP.NET websites and provides really simple tried and tested solutions to solve the same. This book is less of theory and more of real world code and ASP.NET tips and tricks. Great job by Omar.

Click here for more info on this book or even better, buy this book right away from Amazon here :-)

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Using sp_depends to find all Stored Procedures which reference / use a Table

raj — Sun, 20 Jan 2008 14:10:00 GMT

We can use the sp_depends system stored procedure to find all stored procedures which reference / use a particular table. The following T-SQL command will return a list of all database objects which are referencing / using the Products table:

EXEC sp_depends Products

Since the result set(s) returned by executing the above T-SQL command consists of all database objects (and not only stored procedures) which depend upon the Products table, we need to only look at the records which have type as "stored procedure" to know of all stored procedures which reference / use the Product table. Similarly, we need to only look at the records which have type as "view" to know of all views which reference / use the Products table.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Using sp_fkeys to find all Foreign Keys pointing to a Table

raj — Sun, 20 Jan 2008 12:50:00 GMT

We can use the sp_fkeys system stored procedure to find all foreign keys which point to a particular table. The following T-SQL command will return a list of all tables which are referencing the primary key of the Products table:

EXEC sp_fkeys Products

The sp_fkeys system stored procedure comes very handy when dealing with large databases which have hundreds of tables.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

T-SQL Query to Find the Second Highest Column Value in a Table

raj — Thu, 10 Jan 2008 13:53:00 GMT

One of my favorite technical interview question on SQL Server is "What query would you write to find the second highest column value in a table?" The question seems easy, however most developers fail to answer to this. If we had a table named Employee which had a column named Salary and we had to find the second highest Salary in the Employee table, the query for the same would be:

SELECT TOP 1 Salary FROM (SELECT TOP 2 Salary FROM Employee ORDER BY Salary DESC) AS E ORDER BY Salary ASC

If we ran the above query against the Employee table which had the following 5 rows:

1000
2000
3000
4000
5000

The subquery or the inner query would return the top 2 rows in descending Salary order which would be:

5000
4000

The outer query would then select the top 1 row from the subquery results in ascending Salary order which would be:

4000

Note that if we had to get the fourth highest Salary, we could do so by simply changing the subquery from TOP 2 to TOP 4

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Finding Database Size using sp_spaceused Stored Procedure

raj — Wed, 02 Jan 2008 14:33:00 GMT

We can use the sp_spaceused stored procedure to find out exactly how much disk space is currently being used by a database. If we simply execute this stored procedure without passing any parameters, it returns the following 2 result sets:

Result Set 1:

database_name: Name of the current database.
database_size: Size of the current database in megabytes. database_size includes both data and log files.
unallocated space: Space in the database that has not been reserved for database objects.

Result Set 2:

reserved: Total amount of space allocated by objects in the database.
data: Total amount of space used by data.
index_size: Total amount of space used by indexes.
unused: Total amount of space reserved for objects in the database, but not yet used.

code for etetnity !!! is hosted with GoDaddy Shared Hosting Plan which only allows upto 200 MB of database disk space which is really very limited and Community Server can reach this limit in no time. Therefore I have to keep monitoring the database disk space usage regularly. However, since GoDaddy does not provide Remote Desktop or Enterprise Manager / Management Studio access to the database server, the only way to know this is by executing the sp_spaceused stored procedure through GoDaddy's web based Query Analyzer or through a custom built ASP.NET web page which executes this stored procedure using ADO.NET. You can use the same technique if you face similar restrictions by your hosting provider.

For more info on the sp_spaceused stored procedure, click here.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Installing Community Server 2007 with GoDaddy Shared Hosting Plan

raj — Wed, 02 Jan 2008 12:12:00 GMT

Planning to launch a new Community Server 2007 website with GoDaddy Shared Hosting Plan? Or facing problems setting up the same? If you wish to save yourself all the hassles, download and read this excellent CS 2007 Installation Guide for GoDaddy Shared Hosting Plan by Dave Stokes here. I had a hard time setting up my CS 2007 website @ code for eternity !!!, but Dave's Installation Guide came to the rescue. Thanks for the excellent work Dave.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Developing Facebook Applications using Facebook Developer Toolkit for .NET

raj — Wed, 26 Dec 2007 13:33:00 GMT

You can now develop windows based or web based Facebook Applications using your favorite .NET language, be it C# or VB.NET. All you need is a Facebook account, Visual Studio Express and the Facebook Developer Toolkit for .NET. Information about the Facebook Developer Toolkit can be found here. The tooIkit makes it incredibly easy to develop Facebook Applications based on the Facebook Platform. The toolkit also includes WPF and LINQ examples. I would strongly recommend you to check out the following links before going ahead and downloading the toolkit:

1) Video: Facebook Developer Toolkit Walkthrough (Windows Forms)
2) Video: Facebook Developer Toolkit Walkthrough (ASP.NET)
3) Facebook Quickstarts

Detailed information on the Facebook Platform can be found here.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Handling ASP.NET Session Variables Efficiently

raj — Wed, 19 Dec 2007 16:32:00 GMT

One of the most common mistakes ASP.NET developers make is while accessing session variables. Have a look at the code below:

C#:

    // Writing to session variable
    Session["UserCountry"] = ddlUserCountry.SelectedValue;

    // Reading from session variable
    string userCountry = Session["UserCountry"].ToString();

VB:

' Writing to session variable
Session("UserCountry") = ddlUserCountry.SelectedValue

' Reading from session variable
Dim userCountry As String = Session("UserCountry").ToString()

I have seen such code across multiple aspx and ascx code behind pages and it is a disaster waiting to happen and has many drawbacks as follows:

1) If a session variable is read before it has been assigned or if the current session times out, it will result in NullReferenceException as no null checking happens before reading from session variable.

2) A simple spelling mistake of the key name used to identify the session variable ("UserCountry" in above example) will result in NullReferenceException (if no null checking is being done) or incorrect data (if null checking is being done).

3) In large ASP.NET projects where many developers are coding at the same time, very often two developers end up using the same key names for two different session variables meant for two different purposes. I have seen developers use the wildest key names for session variables like "Name" which is so common, it can be used by one developer to save the user's first name, and by another developer to save the user's user name. When such a situation arises, one of the session variable's key name would have to be changed across multiple aspx and ascx code behind pages, making sure that the other session variable sharing the same key name but meant for a different purpose is not changed by accident. This will result in complete chaos, and debugging and testing for such changes becomes a nightmare.

4) There is no easy way to track the usage of session variables, their key names, their data types, the approximate memory being used per session, etc.

However, with just a few extra lines of code and effort, we can get rid of above problems. To address above problems, we can create a single static / shared class (lets call it SessionHandler) which exposes all session variables through strongly typed static / shared properties. No aspx and ascx code behind pages should ever access session variables directly but instead access the strogly typed static / shared properties of the SessionHandler class. All the code to access session variables should exist ONLY in the SessionHandler class. Also, the SessionHandler class should use string variables to save key names of different session variables it exposes in order to avoid spelling mistakes. Have a look at the code below:

C#:

    // Static / shared class for handling session variables
    public static class SessionHandler
    {

        // Declare a string variable to hold the key name of the session variable
        // and use this string variable instead of typing the key name
        // in order to avoid spelling mistakes
        private static string _userCountryKey = "UserCountry";

        // Declare a static / shared strongly typed property to expose session variable
        public static string UserCountry
        {

            get
            {

                // Check for null first
                if (HttpContext.Current.Session[SessionHandler._userCountryKey] == null)
                {
                    // Return an empty string if session variable is null
                    return string.Empty;
                }
                else
                {
                    return HttpContext.Current.Session[SessionHandler._userCountryKey].ToString();
                }

            }

            set
            {
                HttpContext.Current.Session[SessionHandler._userCountryKey] = value;
            }

}

VB:

' Static / shared class for handling session variables
Public Class SessionHandler

        ' Declare a string variable to hold the key name of the session variable
        ' and use this string variable instead of typing the key name
        ' in order to avoid spelling mistakes
        Private Shared _userCountryKey As String = "UserCountry"

' Declare a static / shared strongly typed property to expose session variable
Public Shared Property UserCountry() As String

Get

                ' Check for null first
                If (HttpContext.Current.Session(SessionHandler._userCountryKey) Is Nothing) Then
                    ' Return an empty string if session variable is null
                    Return String.Empty
                Else
                    Return HttpContext.Current.Session(SessionHandler._userCountryKey).ToString()
                End If

End Get

            Set(ByVal value As String)
                HttpContext.Current.Session(SessionHandler._userCountryKey) = value
            End Set

End Property

End Class

Once we have the SessionHandler class in place, all aspx and ascx code behind pages can access session variables through this class like below. Notice that we dont access session variables directly anymore and let the SessionHandler class do all the required work to access session variables.

C#:

    // Writing to session variable
    SessionHandler.UserCountry = ddlCountry.SelectedValue;

    // Reading from session variable
    string userCountry = SessionHandler.UserCountry;

VB:

' Writing to session variable
SessionHandler.UserCountry = ddlUserCountry.SelectedValue

' Reading from session variable
Dim userCountry As String = SessionHandler.UserCountry

Now since all the code to access session variables exists in one single class, it becomes really easy to track their usage, their key names, their data types, the approximate memory being used per session, etc. Also notice how easy it would be to change the key name of a session variable if required. All you would have to do is change the value of one private static / shared variable ("_userCountryKey" in above example). Also, we can be 100% sure that we are not using duplicate key names for multiple session variables by simply checking the value of all existing private static / shared string variables being used to save key names by the SessionHandler class.

Note: We can use the same above architecture (with slight changes to code) to access data from ASP.NET Cache as well as Application Settings. I will blog about it in a future post.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~

Difference between Silverlight Version 1.0 and Silverlight Version 1.1

raj — Tue, 18 Dec 2007 13:03:00 GMT

A lot of my friends who want to get started with Silverlight development keep asking me what's the difference between Silverlight 1.0 and Silverlight 1.1? Which version should they use? Which version supports what?

The primary difference between the two versions is: you can only use JavaScript to create Silverlight applications in version 1.0, however you can use your favorite language, be it C#, VB, IronRuby or IronPython to create Silverlight applications in version 1.1.

For detailed information on the features of Silverlight versions 1.0 and 1.1, click here.

Cheers,
Raj

~~~ CODING FOR ETERNITY !!! ~~~