Работа с Datagridview, Dataset, Update

DataSet detDataSet = new DataSet();
        SqlDataAdapter SqlDataAdapter1 = new SqlDataAdapter();
 
        private void button3_Click(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection(connectstr);
 
            conn.Open();
 
            detDataSet.CaseSensitive = true;
 
            SqlCommand SqlSelectCommand1 = new SqlCommand("Select * from DET", conn);
 
 
            SqlDataAdapter1.SelectCommand = SqlSelectCommand1;
            SqlDataAdapter1.TableMappings.Add("Table", "DET");
 
            SqlDataAdapter1.Fill(detDataSet, "DET");
            SqlSelectCommand1.ExecuteNonQuery();
            dataGridView1.DataSource = detDataSet;
            dataGridView1.DataMember = "DET";
            conn.Close();
        }
        private void button6_Click(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection(connectstr);
            conn.Open();
            SqlCommand SqlUpdateCommand1 = new SqlCommand("UPDATE DET", conn);
            SqlDataAdapter1.UpdateCommand = SqlUpdateCommand1;
            SqlDataAdapter1.Update(detDataSet, "DET");
conn.Close();
        }

SqlCommand SqlUpdateCommand1 = new SqlCommand("UPDATE DET", conn);