validation for user for values

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C#

i want to validate user when he give wrong userid the record should first match with database value and then check it userid is matching if user is not matching then the it should give message wrong userid

i have tired its code but it gives me error please tell me the correct code


//button click event i call this function
BindSponcor();

//function i wrote


private void BindSponcor()
{
DataTable dt = new DataTable();
string query = "SELECT * FROM Registration_Master WHERE sponcorid='" + txtsponcorid.Text.ToString() + "'";
dt = DBHelper.SQLHelper.getTable(query.ToString());
try
{
if ((dt.Rows[0]["sponcorid"].ToString() == txtsponcorid.Text) && (dt.Rows[0]["sponcorname"].ToString() == txtsponcorname.Text.ToString()))
{



}
else
{
String csname = "PopupScript";
Type cstype = this.GetType();
ClientScriptManager cs = Page.ClientScript;
if (!cs.IsStartupScriptRegistered(cstype, csname))
{
String cstext = "confirmVerify()";
cs.RegisterStartupScript(cstype, csname, cstext, true);
}
}


}
catch (Exception ex)
{
throw ex;

}

}