how to find duplicate records

See more:

.NET3.5

C#

.NET

SQL-Server

WPF

Hi,

In my project I want to prevent the duplicate records to the database at inserting time

I wrote the code as follows




try
{
SqlCommand cmd = new SqlCommand();

//This is the query to check the duplicate

String str2 = "select code from state where code='" + this.txtstatecode.Text + "'";
cmd.CommandText = str2;
cmd.Connection = conn;
cmd.ExecuteNonQuery();

//This is the line I wrote to block the duplicate data


if (cmd.ToString ()=="")
{
String str = "insert into State(Code,Name)values ('" + this.txtstatecode.Text + "','" + this.txtstatename.Text + "')";

cmd.CommandText = str;
cmd.Connection = conn;
cmd.ExecuteNonQuery();

DataTable dt = new DataTable();
String str1 = "select code,name from State";// where code='" + this.txtstatecode.Text + "'";
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = str1;
SqlDataAdapter adp = new SqlDataAdapter(cmd);
SqlCommandBuilder cb = new SqlCommandBuilder(adp);

adp.Fill(dt);
bs.DataSource = dt;
statedg5.ItemsSource = bs;
adp.Update(dt);
this.statedg5.Items.Refresh();
}
else
{
System.Windows.MessageBox.Show ("Record already existing");
}

}
catch (Exception e1)
{
System.Windows.MessageBox.Show(e1.Message);
}




But the output is always "Record already existing" even for new records



Pls correct me the error