2

因此，我试图通过详细说明我在网上找到的一个示例来动态添加和删除页面上的用户控件，该示例展示了如何动态添加用户控件。但我似乎无法让移除工作正常进行。我遵循的程序大致是......

  • 在主页中，当单击添加按钮时，我创建一个用户控件并将其deleteBtnClk事件实例分配给 method deleteBtn_Click(object sender, EventArgs e)，我ucSimpleControl_deleteBtnClk从后面的主页代码中传递方法

    protected void btnAddControl_Click(object sender, EventArgs e)
{
    // Create instance of the UserControl SimpleControl
    usercontrols.SimpleControl ucSimpleControl =
      LoadControl("~/usercontrols/SimpleControl.ascx")
      as usercontrols.SimpleControl;

    …………

        ucSimpleControl.deleteBtnClk +=
        new usercontrols.deleteBtn_Click(ucSimpleControl_deleteBtnClk);

我也这样做是方法后面的代码CreateUserControl(string controlID)，它是从OnPreInit方法调用的......

  protected override void OnPreInit(EventArgs e)
        {
  ...
  ...
  ...
        if ((control != null && control.ClientID ==
                        btnAddControl.ClientID) || createAgain)
        {
        ...
        ...
        ...

            CreateUserControl(controlID);
        }

我的用户控件中删除按钮的 OnClick 方法设置为 deleteBtn_Click

  protected void deleteBtn_Click(object sender, EventArgs e)
    {
        onDelBtnClk(e);
    }

它调用虚拟方法 onDelBtnClk

   protected virtual void onDelBtnClk(EventArgs e)
        {
            deleteBtnClk(this, e);
        }

并将 this 和 eventargs 传递给委托，在用户控件创建和呈现时将其分配给方法 ucSimpleControl_deleteBtnClk 后面的代码

 void ucSimpleControl_deleteBtnClk(object sender, EventArgs e)
        {
            usercontrols.SimpleControl ucSimpleControl =
                ((usercontrols.SimpleControl)(sender));
            ucSimpleControl.Parent.Controls.Remove(ucSimpleControl);
            Session.Remove((ucSimpleControl.Num).ToString());
            CreateUserControl(controlID);
        }

在这里，我尝试通过获取父控件并以发送方用户控件作为参数调用 Controls.Remove 方法来删​​除用户控件。然后我从 Session 中移除与用户控件关联的键值对，最后再次调用 CreateUserControl 来渲染 Session 中的所有用户控件。但是这种行为很奇怪，只删除了最近创建的用户控件，而不是与单击的删除按钮关联的那个，而且在我删除一个用户控件后，我不能添加超过当时存在的用户控件的数量这页纸。例如，如果页面上有 5 个用户控件，我删除了一个，然后尝试添加更多，我将无法添加超过 5 个，尽管我应该可以添加无限多个。这是完整的来源...

显示页面.aspx.cs

namespace UserControls4
{
    public partial class DisplayPage : System.Web.UI.Page
    {
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnAddControl_Click(object sender, EventArgs e)
    {
        // Create instance of the UserControl SimpleControl
        usercontrols.SimpleControl ucSimpleControl =
          LoadControl("~/usercontrols/SimpleControl.ascx")
          as usercontrols.SimpleControl;

        // Set the Public Properties
        ucSimpleControl.FirstName.Text = "Milind";
        ucSimpleControl.LastName.Text = "Chavan";

        //Create Event Handler for btnPost Click 
        ucSimpleControl.btnPostClk +=
                new usercontrols.btnPost_Click(ucSimpleControl_btnPostClk);
        /////////////////////////////////////////////////////////////////////////////////////////////////////////////
        ucSimpleControl.deleteBtnClk +=
            new usercontrols.deleteBtn_Click(ucSimpleControl_deleteBtnClk);
        /////////////////////////////////////////////////////////////////////////////////////////////////////////////

        //Add the SimpleControl to Placeholder
        Placeholder1.Controls.Add(ucSimpleControl);

        // Add the instance of the SimpleControl to Session Variable
        Session.Add((Session.Count + 1).ToString(), ucSimpleControl);

        // Set createAgain = true
        createAgain = true;
    }

    void ucSimpleControl_btnPostClk(object sender, EventArgs e)
    {
        usercontrols.SimpleControl ucSimpleControl =
                    ((usercontrols.SimpleControl)(sender));
        lblUser.Text = "Welcome " + ucSimpleControl.FirstName.Text +
                       " " + ucSimpleControl.LastName.Text;
    }

    ///////////////////////////////////////////////////////////////////////////////////////////////////////
    void ucSimpleControl_deleteBtnClk(object sender, EventArgs e)
    {
        usercontrols.SimpleControl ucSimpleControl =
            ((usercontrols.SimpleControl)(sender));
        ucSimpleControl.Parent.Controls.Remove(ucSimpleControl);
        Session.Remove((ucSimpleControl.Num).ToString());
        CreateUserControl(controlID);
    }
    ////////////////////////////////////////////////////////////////////////////////////////////////////////

    // Declare 2 variable to handle user control after postback
    const string controlID = "MyUserControl";
    static bool createAgain = false;

    protected Control GetPostBackControl(Page page)
    {
        Control control = null;
        try
        {
            string ctrlName = page.Request.Params.Get("__EVENTTARGET");

            if (ctrlName != null && ctrlName != String.Empty)
            {
                control = page.FindControl(ctrlName);
            }
            else
            {
                ContentPlaceHolder cph =
                  (ContentPlaceHolder)page.FindControl("Main");
                for (int i = 0, len = page.Request.Form.Count; i < len; i++)
                {
                    string[] ctl = page.Request.Form.AllKeys[i].Split('$');
                    if (ctl.Length > 3)
                    {
                        control = cph.FindControl(ctl[2])
                                  as System.Web.UI.WebControls.Button;
                    }

                    if (control != null) break;
                }
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
        return control;
    }

    protected override void OnPreInit(EventArgs e)
    {
        base.OnPreInit(e);

        Control control = GetPostBackControl(this.Page);

        // Check if the postback is caused by the button 
        // Titled "Click to Create a Dynamic Control"
        // OR
        // createAgain field is true 
        // which means a call is made to the server while the 
        // user control is active  

        if ((control != null && control.ClientID ==
                        btnAddControl.ClientID) || createAgain)
        {
            //should be set before the CreateUserControl method
            createAgain = true;

            CreateUserControl(controlID);
        }
    }

    protected void CreateUserControl(string controlID)
    {
        // createAgain field is set to true in the OnPreInit method
        // when the 'Create User Control' button is clicked 

        // the createAgain field is used to check if the
        // user control is on the page before the call 
        // if so create the control again and add it to the
        // Control Hierarchy again
        try
        {
            if (createAgain && Placeholder1 != null)
            {
                if (Session.Count > 0)
                {
                    Placeholder1.Controls.Clear();
                    int simpleControlCount = 0;
                    for (int i = 0; i < Session.Count; i++)
                    {
                        switch (Session[i].ToString())
                        {
                            case "ASP.usercontrols_simplecontrol_ascx":
                                {
                                    // Keep count of all SimpleControls
                                    simpleControlCount++;
                                    // Create instance of the UserControl SimpleControl
                                    usercontrols.SimpleControl ucSimpleControl =
                                      LoadControl("~/usercontrols/SimpleControl.ascx")
                                      as usercontrols.SimpleControl;

                                    // Set the Public Properties
                                    ucSimpleControl.FirstName.Text =
                                      ((usercontrols.SimpleControl)(Session[i])).FirstName.Text;
                                    ucSimpleControl.LastName.Text =
                                      ((usercontrols.SimpleControl)(Session[i])).LastName.Text;
                                    ucSimpleControl.Num = simpleControlCount;

                                    //Create Event Handler for btnPost Click 
                                    ucSimpleControl.btnPostClk +=
                                      new usercontrols.btnPost_Click(ucSimpleControl_btnPostClk);

                                    /////////////////////////////////////////////////////////////////////////////////////////////////////////
                                    ucSimpleControl.deleteBtnClk +=
                                         new usercontrols.deleteBtn_Click(ucSimpleControl_deleteBtnClk);
                                    //////////////////////////////////////////////////////////////////////////////////////////////////////////

                                    //Add the SimpleControl to Placeholder
                                    Placeholder1.Controls.Add(ucSimpleControl);
                                    break;
                                }
                        }
                    }
                }
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

}

}

显示页面.aspx

<head id="Head1" runat="server">
    <title>This is example of how to add usercontrol dynamically</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
            <asp:Button ID="btnAddControl" runat="server" 
              Text="Click to add SimpleControl" 
              onclick="btnAddControl_Click" />
            <br />
            <asp:PlaceHolder runat="server" 
           ID="Placeholder1" ></asp:PlaceHolder>
            <br />
            <asp:Label ID="lblUser" 
              runat="server"></asp:Label>
    </div>
    </form>
</body>
</html>

简单控制.ascx.cs

namespace UserControls4.usercontrols
{
    public delegate void btnPost_Click(object sender, System.EventArgs e);
    public delegate void deleteBtn_Click(object sendre, System.EventArgs e);

    public partial class SimpleControl : System.Web.UI.UserControl
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        private int num;

        #region Public Event

        public event btnPost_Click btnPostClk;
        public event deleteBtn_Click deleteBtnClk;

        #endregion

        #region Public Properties

        public TextBox FirstName
        {
            get
            {
                return txtFirstName;
            }
            set
            {
                txtFirstName = value;
            }
        }

        public TextBox LastName
        {
            get
            {
                return txtLastName;
            }
            set
            {
                txtLastName = value;
            }
        }

        public int Num
        {
            get { return this.num; }
            set { this.num = value; }
        }
        #endregion

        #region Vitual Methods

        protected virtual void OnbtnDelQtnMrClk(EventArgs e)
        {
            // Call btnPost_Click event delegate instance
            btnPostClk(this, e);
        }

        /// ///////////////////////////////////////////////////////////////////////////////////////
        protected virtual void onDelBtnClk(EventArgs e)
        {
            deleteBtnClk(this, e);
        }

        /// /////////////////////////////////////////////////////////////////////////////////////////

        #endregion

        protected void btnPost_Click(object sender, EventArgs e)
        {
            //Call Virtual Method
            OnbtnDelQtnMrClk(e);
        }

        ///////////////////////////////////////////////////////////////////////////////////////////
        protected void deleteBtn_Click(object sender, EventArgs e)
        {
            onDelBtnClk(e);
        }

    }
}

简单控制.ascx

<table>
    <tr>
        <td><asp:Label ID="label1" runat="server" 
            Text="First Name" ></asp:Label></td>
        <td> <asp:TextBox ID="txtFirstName" 
            runat="server"></asp:TextBox></td>
    </tr>
     <tr>
        <td><asp:Label ID="label2" runat="server" 
           Text="Last Name" ></asp:Label></td>
        <td> <asp:TextBox ID="txtLastName" 
           runat="server"></asp:TextBox></td>
    </tr>
    <tr>
        <td><asp:Button ID="btnPost"  runat="server" 
            Text="Send Info" OnClick="btnPost_Click" />
        </td>
    </tr>
</table>
<obout:SuperForm ID="UserControlSuperForm" 
    Width="630" Title="SuperForm"
    AutoGenerateRows="false"
    RunAt="server"
    DefaultMode="Insert"
    FolderStyle="styles/black_glass">
    <Fields>
        <obout:TemplateField HeaderText="SuperForm">
            <EditItemTemplate>
                <asp:TextBox ID="superFormTxt" runat="server"></asp:TextBox>
            </EditItemTemplate>
        </obout:TemplateField>
    </Fields>
</obout:SuperForm>
<asp:Button ID="removeBtn" runat="server" Text="Remove" OnClick="deleteBtn_Click"/>
4

1 回答 1

0

除了 El Ronnoco 的评论，动态添加和删除控件需要在回发期间添加每个控件，但更重要的是，每个控件都有唯一的 ID。ASP.NET 运行时按 ID 连接事件，因此如果您添加的每个控件都没有唯一 ID，则不会触发事件。

于 2013-01-31T21:34:55.957 回答