What happen with my codes???

Question

Hi!

 

I wrote these codes to doesnt allow duplication records in my table.  But I have a bugg and displaying error message on this line: 

int numRecords = (int)comm.ExecuteScalar(); 

 

error message: 

ExecuteScalar: Connection property has not been initialized.

 

My codes:

 

private void button1_Click(object sender, EventArgs e)

{

conn = new OleDbConnection(connstr);

comm = new OleDbCommand();

conn.Open();

connstr = "SELECT COUNT(*) FROM Not_duplicated_datas WHERE [username] = @username";

comm.CommandText = connstr;

comm.Parameters.Clear();

comm.Parameters.AddWithValue("@username", textBox1.Text);

int numRecords = (int)comm.ExecuteScalar();// the bugg it's here

if (numRecords == 0)

{

connstr = "INSERT INTO Not_duplicated_datas([username],[fillingcode],[branch],[department],[agency])VALUES(@username,@fillingcode,@branch,@department,@agency)";

comm.CommandText = connstr;

comm.Parameters.Clear();

comm.Parameters.AddWithValue("@username", textBox1.Text);

comm.Parameters.AddWithValue("@fillingcode", textBox2.Text);

comm.Parameters.AddWithValue("@branch", textBox3.Text);

comm.Parameters.AddWithValue("@department", textBox4.Text);

comm.Parameters.AddWithValue("@agency", textBox5.Text);

comm.ExecuteNonQuery();

MessageBox.Show("Created Successfully ..");

}

else

{

MessageBox.Show("A record with a user name of {0} already exists", textBox1.Text);

}

conn.Close();