ASP.NET

public partial class admin_edit_sach : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            laysach();
        }
    }
    private void laysach()
    {
        int masach = int.Parse(Request.QueryString["id"].ToString());
        String StrCnn = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + Server.MapPath("~/App_Data/QLBansach.mdb");
        OleDbConnection cnn = new OleDbConnection(StrCnn);
        cnn.Open();
        OleDbCommand cmd = cnn.CreateCommand();
        cmd.CommandText = "select *  from Sach where MaCD=" + masach;
        OleDbDataAdapter da = new OleDbDataAdapter();
        da.SelectCommand = cmd;
        DataSet ds = new DataSet();
        da.Fill(ds);
        txtTenSach.Text = ds.Tables[0].Rows[0]["Tensach"].ToString();
        DropChuDe.SelectedValue = ds.Tables[0].Rows[0]["MaCD"].ToString();
        DropNXB.SelectedValue = ds.Tables[0].Rows[0]["MaNXB"].ToString();
        txtDonGia.Text = ds.Tables[0].Rows[0]["Dongia"].ToString();
        Calendar1.SelectedDate = ds.Tables[0].Rows[0]["Ngaycapnhat"].ToString;
        FileUpload1.FileName = ds.Tables[0].Rows[0]["Hinhminhhoa"].ToString();
        txtMoTa.Text = ds.Tables[0].Rows[0]["Mota"].ToString();
        cnn.Close();
    }
    protected void Btupdate_Click(object sender, EventArgs e)
    {
        int masach = int.Parse(Request.QueryString["id"].ToString());
        String StrCnn = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + Server.MapPath("~/App_Data/QLBansach.mdb");
        OleDbConnection cnn = new OleDbConnection(StrCnn);
        cnn.Open();
        OleDbCommand cmd = new OleDbCommand();
        cmd.Connection = cnn;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "UPDATE Sach SET Tensach='" + txtTenSach.Text + "','" + DropChuDe.SelectedValue + "','" + DropNXB.SelectedValue + "','" + txtDonGia.Text + "','" + Calendar1.SelectedDate.Day + "/" + Calendar1.SelectedDate.Month + "/" + Calendar1.SelectedDate.Year + "','" + FileUpload1.FileName + "','" + txtMoTa.Text + "' Where MaNXB=" + masach;
        cmd.ExecuteNonQuery();
        cnn.Close();
        Response.Redirect("~/Admin/ds_sach.aspx");
    }
}

ompilation Error
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0428: Cannot convert method group 'GetType' to non-delegate type 'System.DateTime'. Did you intend to invoke the method?

Source Error:

Line 36:         DropNXB.SelectedValue = ds.Tables[0].Rows[0]["MaNXB"].ToString();
Line 37:         txtDonGia.Text = ds.Tables[0].Rows[0]["Dongia"].ToString();
Line 38:         Calendar1.SelectedDate = ds.Tables[0].Rows[0]["Ngaycapnhat"].GetType; // Error
Line 39:         FileUpload1.FileName = ds.Tables[0].Rows[0]["Hinhminhhoa"].ToString();  //Error
Line 40:         txtMoTa.Text = ds.Tables[0].Rows[0]["Mota"].ToString();