Stored procedure does not work!

Question

okay, this is one of the weirdest things i have ever seen...so i have created a registration page to my code which on submit it will fire the following codes
protected void btsSubmit_Click(object sender, EventArgs e)
if (tbxFName.Text.Trim().Length == 0 || tbxLName.Text.Trim().Length == 0 || tbxUsername.Text.Trim().Length == 0 || tbxPassword.Text.Length == 0)
ScriptManager.RegisterStartupScript(this, this.GetType(), "myscript", "ShowNotification('Warning','Please fill the required textboxes');", true);
else
try
string conString = ConfigurationManager.ConnectionStrings["IRELDBCS"].ConnectionString;
using (SqlConnection con = new SqlConnection(conString))
SqlCommand sc = new SqlCommand("spUserRegister", con);
sc.CommandType = CommandType.StoredProcedure;
sc.Parameters.AddWithValue("@a", tbxFName.Text.Trim());
sc.Parameters.AddWithValue("@b", tbxLName.Text.Trim());
sc.Parameters.AddWithValue("@c", tbxUsername.Text.Trim());
sc.Parameters.AddWithValue("@d", tbxPassword.Text);
sc.Parameters.AddWithValue("@e", ddlUserType.SelectedValue);
con.Open();
int ReturnCode = (int)sc.ExecuteScalar();
if (ReturnCode == -1)
ScriptManager.RegisterStartupScript(this, this.GetType(), "myscript", "ShowNotification('Error','This user is already exists.');", true);
else
ScriptManager.RegisterStartupScript(this, this.GetType(), "myscript", "ShowNotification('Success','you registration was successful');", true);
catch
ScriptManager.RegisterStartupScript(this, this.GetType(), "myscript", "ShowNotification('Error','Something went wrong, please try again in a few minutes');", true);
i was using sc.ExecuteNonQuery(); instead of int ReturnCode = (int)sc.ExecuteScalar();
and it was working fine and it was functioning till i have added the part which it stops user from registering with the same email address which is 
int ReturnCode = (int)sc.ExecuteScalar();
if (ReturnCode == -1)
ScriptManager.RegisterStartupScript(this, this.GetType(), "myscript", "ShowNotification('Error','This user is already exists.');", true);
else
ScriptManager.RegisterStartupScript(this, this.GetType(), "myscript", "ShowNotification('Success','you registration was successful');", true);
and this is my stored procedure
USE [dbo.IrELearn]
GO
/****** Object: StoredProcedure [dbo].[spUserRegister] Script Date: 04/01/2014 19:35:08 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[spUserRegister]
@a nvarchar(30),
@b nvarchar(50),
@c nvarchar(150),
@d nvarchar(30),
@e smallint
as
BEGIN
declare @Count int
declare @ReturnCode int
SELECT @Count = COUNT(Username)
FROM tbl_Users WHERE Username = @C
IF @Count > 0
Begin
Set @ReturnCode = -1
End
Else
Begin
Set @ReturnCode = 1
INSERT INTO tbl_Users (FirstName, LastName, Username, Password, UserType) VALUES (@a,@b,@a,@b,@e)
End
SELECT @ReturnCode as ReturnValue
END
now users cant register anymore and when i tried to debug and find where the problem is, it completely skips the "if" section after 
int ReturnCode = (int)sc.ExecuteScalar();
im not sure whats goin on!! can anyone find out what the problem is?
thank you in advance

Answer 1

Can you try to replace the statement in the Stored Proc
SELECT @ReturnCode as ReturnValue
with
RETURN @ReturnCode
The SELECT statement returns the value as a dataset but the RETURN statement returns it as a Return Code for success/failure of the Stored Proc execution.
Normally RETURN(0) i.e. a zero is returned as a default for success and a non-zero value is returned for a failure. But don't obther about the values at this time, just try the RETURN statement.
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