在运行时将控件从 .cs 文件添加到 asp .net 表单

发布于 2024-11-18 12:52:15 字数 380 浏览 1 评论 0原文

我有一个网站（使用 asp .net 构建），我想在运行时向其中添加一些文本和图片（我之前不知道数量）。
用户选择参数后，单击一个按钮，该按钮调用以下代码（在 .cs 文件中）：

foreach (var car in cars)
{
  Label lbl = new Label ();
  form1.Controls.Add(lbl);
  lbl.Text = car.name;
  Image myImage = new Image ();
  form1.Controls.Add(myImage);
  myImage.ImageUrl = car.imageURL;

}

但是当我运行代码时，我在页面上看不到控件。我错过了什么吗？
谢谢！

原文

I have a site (build with asp .net) and I want to add to it some text and pictures during runtime (I don't know the amount before).
After the user chooses the parameters, he clicks a button which invokes the following code (in the .cs file):

foreach (var car in cars)
{
  Label lbl = new Label ();
  form1.Controls.Add(lbl);
  lbl.Text = car.name;
  Image myImage = new Image ();
  form1.Controls.Add(myImage);
  myImage.ImageUrl = car.imageURL;

}

but when I run the code, I don't see the controls on the page.
am I missing something?
Thanks!

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笑咖 2024-11-25 12:52:15

在设置控件的属性之前，您必须将控件分配给表单。

例如：

foreach (var car in cars){  
  Label lbl = new Label ();
  form1.Controls.Add(lbl); // Create and immediately assign

  lbl.Text = car.name;  // now you can set some properties

  Image myImage = new Image ();
  form1.Controls.Add(myImage);  // Ditto

  myImage.ImageUrl = car.imageURL;
}

更新：

我刚刚创建了一个全新的 Web 应用程序项目，其页面上只有一个按钮；它按预期工作。我建议你做点别的事情。见下文：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

        <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />

    </div>
    </form>
</body>
</html>

以及背后的代码：

namespace WebApplication1 {
    public partial class _Default : System.Web.UI.Page {
        protected void Page_Load(object sender, EventArgs e) {

        }

        protected void Button1_Click(object sender, EventArgs e) {
            for (Int32 i = 0; i < 10; i++) {
                Label lbl = new Label();
                form1.Controls.Add(lbl);
                lbl.Text = "HAHAHAHAH";
            }
        }
    }
}

You have to assign the control to the form BEFORE setting it's properties.

For example:

foreach (var car in cars){  
  Label lbl = new Label ();
  form1.Controls.Add(lbl); // Create and immediately assign

  lbl.Text = car.name;  // now you can set some properties

  Image myImage = new Image ();
  form1.Controls.Add(myImage);  // Ditto

  myImage.ImageUrl = car.imageURL;
}

UPDATE:

I just created a brand new web application project with a page that only had a button on it; it worked as expected. I suggest you have something else going on. See below:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

        <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />

    </div>
    </form>
</body>
</html>

and the code behind:

namespace WebApplication1 {
    public partial class _Default : System.Web.UI.Page {
        protected void Page_Load(object sender, EventArgs e) {

        }

        protected void Button1_Click(object sender, EventArgs e) {
            for (Int32 i = 0; i < 10; i++) {
                Label lbl = new Label();
                form1.Controls.Add(lbl);
                lbl.Text = "HAHAHAHAH";
            }
        }
    }
}

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够钟 2024-11-25 12:52:15

尝试在表单中添加占位符控件。然后不要调用 Form1.Controls.Add(....) 使用 PlaceHolder1.Controls.Add(.....)

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蓝海 2024-11-25 12:52:15

在 Web 窗体上创建动态控件时，必须在 OnInit 或 Page_Load 事件中创建控件并将其添加到控件集合中。

请参考这个问题以解决您的问题。

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夏雨凉 2024-11-25 12:52:15

您可以尝试 AndyPeacock 所说的，但查看您的代码，我认为您需要研究的实际上是 Repeaters 和其他数据绑定控件，如 DataListView。

下面是一个如何使用中继器实现此功能的简单示例：

在您的 ASPX 文件中：

<asp:Repeater ID="RepCars" runat="server">
    <ItemTemplate>
        <%# Eval("name") %>
        <img src='<% Eval("imageURL") %>' alt="" />
    </ItemTemplate>
</asp:Repeater>

在您的 .CS 部分，可能在 Page_Load 中：

   RepCarImages.DataSource = cars;
   RepCarImages.DataBind();

看一下 http://www.w3schools.com/ASPNET/aspnet_repeater.asp

You can try what AndyPeacock says but looking at your code I think what you need to research into is actually Repeaters and other databound controls like DataListView.

Here's a quick example of how you could implement this with a Repeater:

In your ASPX file:

<asp:Repeater ID="RepCars" runat="server">
    <ItemTemplate>
        <%# Eval("name") %>
        <img src='<% Eval("imageURL") %>' alt="" />
    </ItemTemplate>
</asp:Repeater>

And on your .CS part, probably in Page_Load:

   RepCarImages.DataSource = cars;
   RepCarImages.DataBind();

Have a look at http://www.w3schools.com/ASPNET/aspnet_repeater.asp

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罪#恶を代价 2024-11-25 12:52:15

不是答案，但以下精简示例对我有用：

<%@ Page Language="C#" AutoEventWireup="true" %>
<html>
<head runat="server"></head>
<body>
    <form id="form1" runat="server">

        <script runat="server">
        protected void Button1_Click(object sender, EventArgs e)
        {
            var lit = new Literal();
            Controls.Add(lit);
            Controls.Add(new Literal() { Text = "aaaa" });
            lit.Text = "some text -- ";
        }
        </script>

    <asp:Button ID="Button1" runat="server" Text="Button"
      onclick="Button1_Click" />
    </form>
</body>
</html>

那么您似乎没有发布足够的信息来回答您的问题？

Not an answer, but the following stripped-down sample works for me:

<%@ Page Language="C#" AutoEventWireup="true" %>
<html>
<head runat="server"></head>
<body>
    <form id="form1" runat="server">

        <script runat="server">
        protected void Button1_Click(object sender, EventArgs e)
        {
            var lit = new Literal();
            Controls.Add(lit);
            Controls.Add(new Literal() { Text = "aaaa" });
            lit.Text = "some text -- ";
        }
        </script>

    <asp:Button ID="Button1" runat="server" Text="Button"
      onclick="Button1_Click" />
    </form>
</body>
</html>

So it seems you have not posted enough information to answer your question?

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