Hi,
you can give alert message to user by using following way,
First you have to return some result from database when your data is successfully inserted into database then
you can check your result into code behind and show alert message like this,
if Result="SUCCESS"
{
StringBuilder sb = new StringBuilder();
sb.Append("<script type='text/javascript'>");
sb.Append("alert('Successfully Inserted');");
sb.Append("</script>");
ClientScript.RegisterClientScriptBlock(this.GetType(), "Insert Script", sb.ToString());
}
I hope this will help you.
All d best