c# - 複数選択 DataGrid

Question

コードビハインド(C#)でクラス(MultiGrid)を作成したasp.netで複数選択DataGridを作成する必要があります。

namespace Portal
{
public class MultiGrid : DataGrid
{
    // Constructor that sets some styles and graphical properties    
    public MultiGrid()
    {
        AllowMultiSelect = false;
        AllowMultiSelectFooter = false;

        // Set event handlers
        Init += new EventHandler(OnInit);
        ItemCreated += new DataGridItemEventHandler(OnItemCreated);
    }

    // PROPERTY: SelectedItems
    public ArrayList SelectedItems
    {
        get
        {
            if (!AllowMultiSelect) return null;

            ArrayList a = new ArrayList();
            foreach (DataGridItem dgi in Items)
            {
                CheckBox cb = (CheckBox)dgi.Cells[0].Controls[0];
                if (cb.Checked)
                    a.Add(dgi);
            }
            return a;
        }
    }

    // PROPERTY: AllowMultiSelect 
    public bool AllowMultiSelect = false;

    // PROPERTY: AllowMultiSelectFooter 
    public bool AllowMultiSelectFooter = false;

    // METHOD: ClearSelection
    public void ClearSelection()
    {
        foreach (DataGridItem dgi in Items)
        {
            CheckBox cb = (CheckBox)dgi.Cells[0].Controls[0];
            cb.Checked = false;
        }
    }

    ///////////////////////////////////////////////////////////////////
    // Event Handlers        // EVENT HANDLER: Init            
    private void OnInit(Object sender, EventArgs e)
    {
        // Add a templated column that would allow for selection.
        // The item template contains a checkbox. It also features a 
        // templated footer containing links for Unselect/Select all 
        if (AllowMultiSelect)
            AddSelectColumn();
    }

    // EVENT HANDLER: Deselect
    private void OnDeselect(Object sender, EventArgs e)
    {
        ClearSelection();
    }

    // EVENT HANDLER: ItemCreated            
    private void OnItemCreated(Object sender, DataGridItemEventArgs e)
    {
        // Get the newly created item
        ListItemType itemType = e.Item.ItemType;

        ///////////////////////////////////////////////////////////////
        // FOOTER
        if (itemType == ListItemType.Footer && AllowMultiSelectFooter
            && AllowMultiSelect)
        {
            // Look for a link button called "lnkSelect" in the context 
            // of the grid item that represents the footer
            LinkButton lb = (LinkButton)
                e.Item.FindControl("lnkDeselect");

            // Now you hold the living instance of the link 
            // button in the footer and can bind it to any code in the 
            // context of the MultiGrid control
            lb.Click += new EventHandler(OnDeselect);

            // Force ShowFooter to true
            ShowFooter = true;

            // Removes all the cells but the first 
            TableCell cell = e.Item.Cells[0];
            for (int i = 1; i < Columns.Count; i++)
            {
                e.Item.Cells.RemoveAt(1);
            }
            cell.ColumnSpan = Columns.Count;
        }
    }

    ///////////////////////////////////////////////////////////////////
    // Helper Functions

    private void AddSelectColumn()
    {
        // Create the new templated column
        TemplateColumn tc = new TemplateColumn();
        tc.ItemStyle.BackColor = Color.SkyBlue;
        tc.ItemTemplate = new SelectColumnTemplate();
        tc.FooterTemplate = new SelectFooterTemplate();
        Columns.AddAt(0, tc);
    }
}
///////////////////////////////////////////////////////////////////////
// Template Classes

public class SelectColumnTemplate : ITemplate
{
    public void InstantiateIn(Control container)
    {
        CheckBox cb = new CheckBox();
        container.Controls.Add(cb);
    }
}

public class SelectFooterTemplate : ITemplate
{
    public void InstantiateIn(Control container)
    {
        LinkButton lb = new LinkButton();
        lb.Text = "Deselect all";
        lb.ID = "lnkDeselect";
        container.Controls.Add(lb);
    }
}
}

問題: aspx ファイルでこのクラスにアクセスする必要がありますが、「要素 "MultiGrid" は既知の要素ではありません」と表示されます。私のaspxコード。

<%@ Register TagPrefix="expo" Namespace="Portal" Assembly="MultiGrid" %>
<expo:MultiGrid id="grid" runat="server" 
AutoGenerateColumns="false"
AllowMultiSelect="true"
AllowMultiSelectFooter="true"
font-size="x-small" font-names="verdana"
BorderStyle="solid" BorderWidth="1"
GridLines="both">

どんな助けでも大歓迎です。