Technology

iPhoneKicks.com RSS Widget Launched

raj — Mon, 29 Dec 2008 11:34:00 GMT

Check out http://www.iphonekicks.com/docs/widget

New Social Bookmarking Site for iPhone SDK launched

raj — Sun, 07 Dec 2008 09:50:00 GMT

Me and my friend just launched a new social bookmarking site for iPhone SDK. It specialises in iPhone SDK development techniques, technologies and tools including Xcode, iPhone Simulator, Instruments, Interface Builder, SQLite, OpenGL ES, Cocoa.

Check out http://www.iPhoneKicks.com is a community based news site edited by their members.

Cheers,
Raj

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

MSDTC on server '[SERVER NAME]' is unavailable

raj — Fri, 05 Dec 2008 13:14:00 GMT

If your code uses distributed transactions and you get the "MSDTC on server '[SERVER NAME]' is unavailable" error, all you have to do to fix it is go to the Services console on your server and start the Distributed Transaction Coordinator service.

On Vista, you can click on Start > Administrative Tools > Services to go to the Services console.

Cheers,
Raj

~~~ CODING 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 !!! ~~~