Sqldataadapter update from datagridview C# problem

SqlDataAdapter adp;
SqlCommandBuilder cmdBld;
DataTable dtEditMember = new DataTable();

private void butLoadMember_Click(object sender, EventArgs e)
{
    using (SqlConnection conn = new SqlConnection(dbConn))
    {
        conn.Open();
        using (adp = new SqlDataAdapter())
        {
            if (txtEditMemberVehiNo.MaskCompleted)
            {
                adp.SelectCommand = new SqlCommand("Select * From Master Where VehiNo = @VehiNo");
                adp.SelectCommand.Parameters.Add("@VehiNo", SqlDbType.NVarChar).Value = txtEditMemberVehiNo.Text;
            }
            else if (!string.IsNullOrWhiteSpace(txtEditMemberCustName.Text))
            {
                adp.SelectCommand = new SqlCommand("Select * From Master Where CustName = @CustName");
                adp.SelectCommand.Parameters.Add("@CustName", SqlDbType.NVarChar).Value = txtEditMemberCustName.Text;
            }

            adp.SelectCommand.Connection = conn;
            adp.Fill(dtEditMember);
        }
    }
    if (dtEditMember.Rows.Count > 0)
    {
        dgvEditMember.DataSource = dtEditMember;
        dgvEditMember.Columns["VehiNo"].HeaderText = "Vehicle No";

        butLoadMember.Enabled = false;
        butUpdateMember.Enabled = true;
    }
    else
    {
        txtEditMemberVehiNo.Clear();
        txtEditMemberCustName.Clear();
        dgvEditMember.Columns.Clear();
        MessageBox.Show("Member Not Found.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Information);
    }

}

private void butUpdateMember_Click(object sender, EventArgs e)
{

    cmdBld = new SqlCommandBuilder(adp);
    if (dtEditMember.GetChanges() != null)
    {
        adp.Update(dtEditMember);
        MessageBox.Show("Changes Done.");
    }
}