UserControl 中的 Web 控件为空？

发布于 2024-11-04 08:11:04 字数 1353 浏览 3 评论 0原文

我构建了一个小型用户控件，它本质上是一个 DropDownList，其中包含一些基于目标属性设置的预设值。

代码如下：

public partial class Selector : System.Web.UI.UserControl
{
    public string SelectedValue { get {return this.ddl.SelectedValue; } }
    public int SelectedIndex { get { return this.ddl.SelectedIndex; } }
    public ListItem SelectedItem { get { return this.ddl.SelectedItem; } }
    private string target;
    public string Target { get { return this.target; } set { this.target = value; } }
    protected void Page_Load(object sender, EventArgs e)
    {
        ddl.DataSource = target=="Group"?Util.GetAllGroups(Session["sessionId"].ToString()):Util.GetAllUsers(Session["sessionId"].ToString());
        ddl.DataBind();
    }
}

ASP-Markup：

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="Selector.ascx.cs" Inherits="InspireClient.CustomControls.Selector" %>
<asp:DropDownList runat="server" ID="ddl">
</asp:DropDownList>

如果我将选择器插入 aspx 页面，它就可以正常工作。示例：

<SCL:Selector Target="Group" runat="server" />

但是，如果我像这样以编程方式添加它，则

ctrl = new Selector();
ctrl.Target = "User";

DropDownList“ddl”为空，并且应用程序（逻辑上）会引发错误。 Page_Load 是做这种事情的错误方法吗？我做错了什么？

我应该补充一点，“ctrl”是动态类型，不确定这是否与它有关。

提前致谢！

丹尼斯

原文

I've built a small User Control which is essentially a DropDownList with some preset Values based on what the Target-Property is set on.

Here's the Code:

public partial class Selector : System.Web.UI.UserControl
{
    public string SelectedValue { get {return this.ddl.SelectedValue; } }
    public int SelectedIndex { get { return this.ddl.SelectedIndex; } }
    public ListItem SelectedItem { get { return this.ddl.SelectedItem; } }
    private string target;
    public string Target { get { return this.target; } set { this.target = value; } }
    protected void Page_Load(object sender, EventArgs e)
    {
        ddl.DataSource = target=="Group"?Util.GetAllGroups(Session["sessionId"].ToString()):Util.GetAllUsers(Session["sessionId"].ToString());
        ddl.DataBind();
    }
}

ASP-Markup:

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="Selector.ascx.cs" Inherits="InspireClient.CustomControls.Selector" %>
<asp:DropDownList runat="server" ID="ddl">
</asp:DropDownList>

If I insert my Selector into an aspx-Page it works just fine.
Example:

<SCL:Selector Target="Group" runat="server" />

However, If I programmatically add it like this

ctrl = new Selector();
ctrl.Target = "User";

the DropDownList "ddl" is null and the application (logically) throws an error. Is Page_Load the wrong Method to do such a thing? What am I doing wrong?

I should add, "ctrl" is of type dynamic, not sure if this has anything to do with it.

Thanks in advance!

Dennis

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長街聽風 2024-11-11 08:11:04

由于您动态添加用户控件而不是“简单”Web 控件，因此您应该使用 LoadControl() 方法来实例化它：

protected void Page_Load(object sender, EventArgs e)
{
    Selector yourControl = (Selector) LoadControl("Selector.ascx");
    yourControl.Target = "User";
    Controls.Add(yourControl);
}

Since you're dynamically adding a user control and not a "simple" web control, you should use the LoadControl() method to instantiate it:

protected void Page_Load(object sender, EventArgs e)
{
    Selector yourControl = (Selector) LoadControl("Selector.ascx");
    yourControl.Target = "User";
    Controls.Add(yourControl);
}

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