Checking a value in database

Question

Hi guys, I need help on checking the value in database, for example
if the user name already exist in the database, the user cant choose the same name.
can anyone help me on how to achieve that in C#
thanks.........

Dipa Ahuja · Answer

suppose you want to check the field "id" then:
private string dq = "select * from users";     SqlDataAdapter da=new SqlDataAdapter (dq, ); DataSet ds=new DataSet(); da.Fill(ds);
// private void btnadd_Click(object sender, EventArgs e) {
int newid; newid = Convert.ToInt32(txtid.Text.ToString());
if (! checkIfUnique (newid))             {                 MessageBox.Show("ID Already exists!");                 txtid.Focus();                 return;             } //insert operation }  private bool checkIfUnique(int newid)         {             int oldid;             foreach (DataRow r in ds.Tables["users"].Rows)             {                 oldid = Convert.ToInt32(r["id"]);                 if (oldid == newid)                     return false;             }             return true;         }