Database Is Not Updated

I am trying to insert data to a simple table using SQL express

However , I can see the data saved in the DataSet but not in the actual database.

If I try to insert the same user again , I got primary key violation ???



Here is the insert function :

string SqlConnection = @"Data Source=.SQLEXPRESS;AttachDbFilename=|DataDirectory|QJ.mdf;Integrated Security=True;User Instance=True";

SqlConnection Conn = new SqlConnection(SqlConnection);

SqlDataAdapter DataAdapter = new SqlDataAdapter("SELECT * FROM USERS", Conn);

SqlCommandBuilder ComandBuilder = new SqlCommandBuilder(DataAdapter);

DataAdapter.InsertCommand = ComandBuilder.GetInsertCommand();

DataAdapter.UpdateCommand = ComandBuilder.GetUpdateCommand();

DataSet DS = new DataSet();

DataAdapter.Fill(DS, "USERS");

DataTable DT = DS.Tables["USERS"];

DataRow DR = DT.NewRow();

DR["NAME"] = txtUserName.Text;

DR["Password"] = txtPass.Text;

DR["Type"] = 1;

DT.Rows.Add(DR);

DataAdapter.Update(DS,"USERS");

DS.AcceptChanges();

Conn.Close();











I dont know what I have done wrong

Please help

Thanks very much