How to check Database on createID form buttonclick

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I am creating windows application in Visual Studio 2008 and database SQL 2005. i was creating login ID and password form but before i want create ID form in that when i am going to click on CreateID button ....it has to first check for previous login ID in SQL database Login table...if Login ID is present then it have to give error for example
" Login ID is already present " ....how to write the code for it...

please help me if anyone knows...

Posted 9-Aug-11 0:02am

nishikant.K

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Herman<T>.Instance · Answer 1 · 2011-08-09T00:10:00

if your Login ID is a a textbox then in the OnClick event of the button:

SQL

string MyCheckQuery = string.Format("SELECT count(0) FROM tblLogin WHERE loginName ='{0}'", textBox1.Text);

That query can be used with an SqlCommand
http://msdn.microsoft.com/en-us/library/877h0y3a.aspx[^]

If the result of the query = 0 then the name is unique, otherwies the result of the query is 1

Shameel · Answer 2 · 2011-08-09T00:06:00

Solution 2

Try this:

SQL

IF EXISTS(SELECT LoginID FROM Users WHERE LoginID = @LoginID)
BEGIN
    RAISERROR('LoginID already exists.', 1,1)
END
ELSE
BEGIN
    INSERT INTO Users(..........)
    VALUES (............)
END

Posted 9-Aug-11 0:06am

Shameel

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nishikant.K 9-Aug-11 6:25am

how to write code in C#.....

please give code in C#

#realJSOP · Answer 3 · 2011-08-09T00:06:00

Solution 1

Let the database do it. If you set the loginID to be a unique column, trying to add an id that already exists will generate an error in the stored procedure which will be reflected to the client app as an exception (or maybe the return value from the stored proc will indicate a problem).

Posted 9-Aug-11 0:06am

#realJSOP