此web用户控件代码有什么问题？

Question

我已经创建了一个简单的web用户控件，并且我已经在页面上注册了它以使用它。

我设置了一些必需的属性，然后调用控件的公共方法

其中我使用了一些按钮，我已经放在我的ascx文件。

当我使用按钮(我的用户控件只有12个按钮)时，我得到空引用异常。

下面是我的用户控件的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace MangoCustomControls
{
    public partial class MangoPagerControl : System.Web.UI.UserControl
    {
        // variables
        private int _totalItemCount;
        private int _currentPageIndex;
        private int _itemsPerPage;
        private int _noOfPages;
        private const int MAX_PAGE_SIZE = 10;
        // event
        public event EventHandler<PagerControlEventArgs> OnPagerItemClicked;
        // methods
        public void BindPager()
        {
            int remainder = _totalItemCount % _itemsPerPage;
            int result = _totalItemCount / _itemsPerPage;

            if (remainder > 0)
            {
                result++;
            }

            _noOfPages = result;

            ShowHideButtonsAndPutTextsOnThem();
        }

        private void ShowHideButtonsAndPutTextsOnThem()
        {
            if (_noOfPages < MAX_PAGE_SIZE)
            {
                btnPrev.Visible = false;
                btnNext.Visible = false;

                for (int i = 1; i <= MAX_PAGE_SIZE; i++)
                {
                    Control ctrl = FindControl(string.Format("btn{0}", i));
                    if (i <= _noOfPages)
                    {
                        ctrl.Visible = true;
                        ((Button)ctrl).Text = string.Format("{0}", i);
                    }
                    else
                    {
                        ctrl.Visible = false;
                    }
                }
            }
            else
            {
                btnPrev.Visible = false;
                btnNext.Visible = true;

                for (int i = 1; i <= MAX_PAGE_SIZE; i++)
                {
                    Control ctrl = FindControl(string.Format("btn{0}", i));
                    ctrl.Visible = true;
                    ((Button)ctrl).Text = string.Format("{0}", i);
                }
            }

        }

        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void OnButtonClick(object sender, EventArgs e)
        {
            Button btn = sender as Button;
            int pageNumber = int.TryParse(btn.Text, out pageNumber) ? pageNumber : -1;
            if (OnPagerItemClicked != null)
            {
                OnPagerItemClicked(this, new PagerControlEventArgs(pageNumber));
            }
        }

        // properties
        public int TotalItemCount
        {
            get { return _totalItemCount; }
            set { _totalItemCount = value; }
        }
        public int ItemsPerPage
        {
            get { return _itemsPerPage; }
            set { _itemsPerPage = value; }
        }
        public int CurrentPageIndex
        {
            get { return _currentPageIndex; }
            set { _currentPageIndex = value; }
        }
    }

    public class PagerControlEventArgs : EventArgs
    {
        public int SelectedPageNumber { get; private set; }

        public PagerControlEventArgs(int selectedPageNumber)
        {
            SelectedPageNumber = selectedPageNumber;
        }
    }
}

设计器文件如下所示：

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="MangoPagerControl.ascx.cs"
    Inherits="MangoCustomControls.MangoPagerControl" %>
<div>
    <table>
        <tr>
            <td>
                <asp:Button ID="btnPrev" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn1" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn2" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn3" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn4" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn5" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn6" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn7" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn8" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn9" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btn10" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
            <td>
                <asp:Button ID="btnNext" runat="server" Text="" OnClick="OnButtonClick" />
            </td>
        </tr>
    </table>
</div>

以及(在页面上)调用控件方法的代码：

 protected void Button2_Click(object sender, EventArgs e)
        {           

                MangoPager.TotalItemCount = 7;
                MangoPager.ItemsPerPage = 2;
                MangoPager.BindPager();

        }

我在网页上注册用户控件，如下所示：

<%@ Register TagPrefix="CustomMango" Namespace="MangoCustomControls" Assembly= "MangoCustomControls" %>

并像这样创建MangoPager控件：

<CustomMango:MangoPagerControl  ID="MangoPager" runat="server" 
        ononpageritemclicked="MangoPagerControl1_OnPagerItemClicked" />

在BindPager()方法中，我得到了btnPrev的空引用异常(所有按钮都是空的)。

deigner文件如下所示：

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated. 
// </auto-generated>
//------------------------------------------------------------------------------

namespace MangoCustomControls {


    public partial class MangoPagerControl {

        /// <summary>
        /// btnPrev control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btnPrev;

        /// <summary>
        /// btn1 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn1;

        /// <summary>
        /// btn2 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn2;

        /// <summary>
        /// btn3 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn3;

        /// <summary>
        /// btn4 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn4;

        /// <summary>
        /// btn5 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn5;

        /// <summary>
        /// btn6 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn6;

        /// <summary>
        /// btn7 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn7;

        /// <summary>
        /// btn8 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn8;

        /// <summary>
        /// btn9 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn9;

        /// <summary>
        /// btn10 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btn10;

        /// <summary>
        /// btnNext control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.WebControls.Button btnNext;
    }
}

请告诉我为什么它是空的，我应该怎么做来解决它？

Answer 1

从Register指令中完全删除命名空间和程序集属性，因为这些属性仅用于服务器控件。要注册用户控件，您必须指定放置ascx文件的Src、TagPrefix和TagName。How to: Include a User Control in an ASP.NET Web Page