Check UserName Availability from database Using JQuery in asp.net

Now Lets create a SQL table and name it to User_Table and to create it you can use Database wizard or you can use this SQL Script

CREATE TABLE [dbo].[User_Table](
  [User_Name] [varchar](30) NOT NULL,
  [First_Name] [varchar](50) NOT NULL,
  [Last_Name] [varchar](50) NOT NULL,
  [Middle_Name] [varchar](50) ,
  [Email_Id] [varchar](70) NOT NULL,
 CONSTRAINT [PK_User_Table] PRIMARY KEY CLUSTERED 
(
  [User_Name] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

Now we have to create one stored procedure to validate the user Name exist in the database or not

CREATE PROCEDURE CheckUserName(  @User_Name VARCHAR(50) )
AS 
BEGIN 

  IF EXISTS (SELECT * FROM User_Table WHERE  [User_Name] = @User_Name ) 

  SELECT '1'; --user name already exist in database

  ELSE 

  SELECT '0'; --user name does not exist in database

END

Now in your .cs file you need to create a PageMethod which  will call the stored procedure and depend upon the user name availability it will return the string message to the JQuery function for displaying message to the user
So there is the Page method
If you see this method is Webservice method which will return the result and this function you can write in your Register.cs page.

You have to add this [System.Web.Services.WebMethod] attribute to the function which will check the username from the database.

In C# Example

[System.Web.Services.WebMethod]
  public static string CheckUserName(string args)
  {

  string returnValue = string.Empty;

  string conString = ConfigurationManager.ConnectionStrings["MyConnection"].ConnectionString;

  SqlConnection sqlConn = new SqlConnection(conString);

  try
  {

  SqlCommand sqlCmd = new SqlCommand("CheckUserName", sqlConn);

  sqlCmd.CommandType = CommandType.StoredProcedure;

  sqlCmd.Parameters.AddWithValue("@User_Name", args.Trim());

  sqlConn.Open();

   int success = int.Parse((sqlCmd.ExecuteScalar().ToString()));

  if(success == 1) // User Name Not Available
  {
  returnValue = "'" + args + "' is already in use.";
  
  }
  else if(success == 0)//User_Name is available
  {
  returnValue = "Available";
  }

  }
  catch
  {
  //Handle Error
  }
  finally
  {
  sqlConn.Close();
  }
  
  return returnValue;
  }

And in VB.NET Sample

 _
Public Shared Function CheckUserName(ByVal args As String) As String

  Dim returnValue As String = String.Empty

  Dim conString As String = ConfigurationManager.ConnectionStrings("MyConnection").ConnectionString

  Dim sqlConn As New SqlConnection(conString)

  Try

  Dim sqlCmd As New SqlCommand("CheckUserName", sqlConn)

  sqlCmd.CommandType = CommandType.StoredProcedure

  sqlCmd.Parameters.AddWithValue("@User_Name", args.Trim())

  sqlConn.Open()

  Dim success As Integer = Integer.Parse((sqlCmd.ExecuteScalar().ToString()))

  If success = 1 Then
  ' User Name Not Available

  returnValue = " '" & args & "' is already in use."
  ElseIf success = 0 Then
  'User_Name is available
  returnValue = "Available"

  End If
  Catch
  'Handle Error
  Finally
  sqlConn.Close()
  End Try

  Return returnValue
End Function

And Now you are done..
Once you run the application you will see an example like this

If the username is available you will see this screen



If user Name is not available you will see this screen



If user has entered less than 5 character you will this see this screen


You can use the above JQuery function to validate any input with Database entry like Email and other stuff. Also if you want to validate on Button click than just change the control id and its event on what you want to validate.

Cheers!!!
Pankaj