How to throw a error in asp.net if already exist

you can create table with unique key on email like

Create Table TblUser
(
Name Varchar(100),
Email Varchar(50)Unique
etc....
)

When you are inserting values in the table first you need to check the email exists or not for the easiest you can use stored procedure like

Create Procedure Sp_RegisterUser
(
@name Varchar(200),
@email Varchar(50),
@message Varchar(200)out
)
As
Begin
if not exists(Select Email From TblUser Where Email=@email)
Begin
Insert Statement
Set @message='User Registered'
End
Else
Begin
Set @message='Email Already Exists'
End
End

Hope this may helps you

Hi

For that you need to check in the database that email is exists or not.If email is exists then you can simply display a error message in the label that email is exists.

Or you can create the unique key on Email,which gives you an error on save for duplication and handle it in the catch block and display that error.

Hope this helps.

thanks