}else if (cmbSuchen.SelectedItem.ToString() == "Firma")
2.            {
3.                con.Open();
4.                var strSQL = "Select kdnr, firma, plz, ort, extra from" & _
  "stammdaten where firma = LIKE '%' + @SEARCH + '%'" ;
5.                DataSet ds = new DataSet();
6.                SqlDataAdapter adapter = new SqlDataAdapter();
7.                adapter.SelectCommand = new SqlCommand(strSQL, con);
8.                adapter.SelectCommand.Parameters.AddWithValue("@SEARCH", "%"  _
  + txtBSuchen.Text + "%");
9.                adapter.Fill(ds, "Stammdaten");
10. 
11.                txtName.Text = ds.Tables[0].Rows[0]["firma"].ToString();
12.                txtKdnr.Text = ds.Tables[0].Rows[0]["kdnr"].ToString();
13.                txtOrt.Text = ds.Tables[0].Rows[0]["ort"].ToString();
14.                txtPlz.Text = ds.Tables[0].Rows[0]["plz"].ToString();
15. 
16.                    //SelectCommand.Parameters.AddWithValue("@query", _
  txtBSuchen.Text);
17.                //adapter2.Fill(ds1, "Stammdaten");
18.                con.Close();
19.                grbSuchen.Visible = false;
20.                grbStamm.Visible = true;
21.            }

adapter.Fill(ds, "Stammdaten");