duplicate name not allow

i have 'user' table:fields are:nameemailidaddressph.nopasswordwhen i insert new data from textbox,it will check whether name is allready exsist or not .if not exsist then allow to enter name in textbox.how to do this?more discription of my problem:when i enter...

Hi Friend..on insertion button click event just do this... con.Open(); MySqlCommand cmd = new MySqlCommand("select * from Your_tableUser where name='"+txtboxName.text+"'", con); MySqlDataReader dr = cmd.ExecuteReader(); if (dr.Read()) { ...