在 foreach 循环内设置用户控件的属性

发布于 2024-08-08 21:59:15 字数 885 浏览 5 评论 0原文

我有一个用户控件，我在多个页面上使用它来显示有关对象的信息。每当我需要使用此用户控件时，我都会调用一个名为 Display 的方法（在用户控件上）并传入一些值。

public void Display(string name, List<Items> items)
{
    // Set a few protected properties so I can display values from the aspx page
}

这工作正常，但现在我需要在 aspx 页面的 foreach 循环内使用此控件。

<% foreach (var c in Categories) { %>
      <uc:ItemsControl runat="server"/>
<% } %>

类别对象具有我本来会传递到 Display 方法中的方法和属性。那么我该如何正确设置这些值呢？

我尝试将用户控件上的属性公开并以这种方式设置它们：

<uc:ItemsControl Items="<%# c.Items %>" 
                 OtherProperty="<%# c.GetProperty() %>" 
                 runat="server"/>

这不起作用，因为发送的属性是空的。如果我使用 <%= 那么它不起作用，实际上会抛出一个错误，因为它无法识别“c”（除非我取消 runat="server" 那么它至少会编译，但它仍然无法工作不过，

执行此操作的正确方法是什么？

编辑：此外，转发器控件可能会使数据绑定更容易，但我宁愿避免使用任何 .NET 控件。

原文

I have a user control that I use on multiple pages to show information about an object. Whenever I need to use this usercontrol, I call a method called Display (on the usercontrol) and pass in some values.

public void Display(string name, List<Items> items)
{
    // Set a few protected properties so I can display values from the aspx page
}

This works fine, but now I need to use this control inside a foreach loop in an aspx page.

<% foreach (var c in Categories) { %>
      <uc:ItemsControl runat="server"/>
<% } %>

The categories object has the methods and properties that I would otherwise pass into the Display method. So how would I properly set the values?

I tried making the properties on the user control public and just setting them in this way:

<uc:ItemsControl Items="<%# c.Items %>" 
                 OtherProperty="<%# c.GetProperty() %>" 
                 runat="server"/>

This doesn't work, because the properties getting sent in are empty. If I use <%= then it doesn't work and actually throws an error because it doesn't recognize 'c' (unless I take off runat="server" then it will at least compile, it still won't work though.

What is the proper way to do this?

Edit: Also, a repeater control might make this easier for databinding, but I'd prefer to avoid the use of any .NET controls.

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

挖个坑埋了你 2024-08-15 21:59:15

在 WebForms 页面中，通常使用 DataBinding 来处理此问题。您可以使用 Repeater 代替 foreach 循环控件，将其 DataSource 属性设置为 <%#Categories%>，然后使用上面后一个示例中的数据绑定语法，但不要使用 c，您需要将 Container.DataItem 转换为控件中的正确类型。像这样：

<%@ Page Language="C#" %>
<script runat="server">
protected void  Page_Load(object sender, EventArgs e)
{
    CategoriesList.DataBind();
}
class Category
{
    public string CategoryName { get; set; }
    public string GetProperty() { return CategoryName; }
    public string[] Items { get { return new string[] {CategoryName + " 1", CategoryName + " 2"}; } }
}
Category[] Categories = new Category[]
{
    new Category { CategoryName = "Shorts" },
    new Category { CategoryName = "Socks" },
    new Category { CategoryName = "Shirts" },
};
</script>
<html>
<body>
<asp:Repeater runat="server" ID="CategoriesList" DataSource="<%# Categories %>">
  <ItemTemplate>
    <uc:ItemsControl 
       Items="<%# ((Category)(Container.DataItem)).Items %>" 
       OtherProperty="<%# ((Category)(Container.DataItem)).GetProperty() %>" 
       runat="server"/>
  </ItemTemplate>       
</asp:Repeater>
</body>
</html>

唯一需要注意的是，您需要在某个地方调用 Repeater 的 DataBind() 方法，通常是在 Page_Load 方法中。

就我个人而言，我一直发现数据绑定很痛苦——对我来说，转换和调用数据绑定的需要都比您上面尝试的 foreach 方法更不自然。这可能是我最喜欢 ASP.NET MVC 的一点——您的 MVC 视图可以更轻松地使用迭代的 foreach 模型，这更简单，恕我直言。也就是说，如果您必须坚持使用 WebForms，则数据绑定与转换是阻力最小的途径。

顺便说一句，您的上述方法不起作用，因为：

runat=server ASP.NET 控件属性无法使用填充
<%= %> 语法——这只是有用的
用于纯文本输出，而不是用于
填写对象属性。
使用数据绑定语法（<%# %>）绝对可以用来填充
在控制属性中，但你需要
将控件包装在数据绑定中
容器（如中继器）并调用
DataBind() 为了得到
发生替换。

In a WebForms page, the way this is usually handled by using DataBinding. Instead of a foreach loop, you can use a Repeater control, set its DataSource property to <%#Categories%>, and then use the data-binding syntax in your latter example above, except instead of c, you'll need to cast Container.DataItem to the proper type in your control. Like this:

<%@ Page Language="C#" %>
<script runat="server">
protected void  Page_Load(object sender, EventArgs e)
{
    CategoriesList.DataBind();
}
class Category
{
    public string CategoryName { get; set; }
    public string GetProperty() { return CategoryName; }
    public string[] Items { get { return new string[] {CategoryName + " 1", CategoryName + " 2"}; } }
}
Category[] Categories = new Category[]
{
    new Category { CategoryName = "Shorts" },
    new Category { CategoryName = "Socks" },
    new Category { CategoryName = "Shirts" },
};
</script>
<html>
<body>
<asp:Repeater runat="server" ID="CategoriesList" DataSource="<%# Categories %>">
  <ItemTemplate>
    <uc:ItemsControl 
       Items="<%# ((Category)(Container.DataItem)).Items %>" 
       OtherProperty="<%# ((Category)(Container.DataItem)).GetProperty() %>" 
       runat="server"/>
  </ItemTemplate>       
</asp:Repeater>
</body>
</html>

The only caveat is you'll need to call the DataBind() method of the Repeater somwhere, typically in the Page_Load method.

Personally, I have always found data-binding to be a pain-- both the casting and the need to call data-bind feel much less natural to me than the foreach method you tried above. That's probably the thing I like best about ASP.NET MVC-- your MVC Views can much more easily use the foreach model of iteration which is much more straightforward, IMHO. That said, if you have to stick with WebForms, databinding-with-casting is the path of least resistance.

BTW, your approaches above didn't work because:

runat=server ASP.NET control properties cannot be filled using
<%= %> syntax-- that's only useful
for plain-text output, not for
filling in object properties.
using data-binding syntax ( <%# %>) can definitely be used to fill
in control properties, but you need
to wrap the control in a data-binding
container (like a Repeater) and call
DataBind() in order to get the
replacement to happen.

回复收藏 0 原文

是你 2024-08-15 21:59:15

我知道这已经很旧了，但我通过谷歌很快发现了这个线程，所以我只需输入这个。

我刚刚在帮助同事时注意到，您可以使用 foreach 中的 UserControls 来执行此操作。请注意，我仅通过他的示例对其进行了测试。

<% foreach (var c in Categories) { %>
<%    MyControl ctrl = (MyControl)FindControl("ucItem"); %>
<%    ctrl.PropertyToChange = c.Property; %>

      <uc:MyControl runat="server" ID="ucItem"/>
<% } %>

如果这不适用于您，至少对其他人可能适用。

I know this is old, but I found this thread through google quite instant so I'll just type this.

I've just noticed when helping a colleague that you could do like this with UserControls in foreach. Note that I've only tested it through his example.

<% foreach (var c in Categories) { %>
<%    MyControl ctrl = (MyControl)FindControl("ucItem"); %>
<%    ctrl.PropertyToChange = c.Property; %>

      <uc:MyControl runat="server" ID="ucItem"/>
<% } %>

If this is not applicable for you at least it might be for others.

回复收藏 0 原文

何以心动 2024-08-15 21:59:15

而贾斯汀·格兰特的回答可能会工作得很好，我们决定只加载用户控件并调用 DisplayResults 方法。

<% ((UserControlType)LoadControl("~/pathToUserControl.ascx"))
       .DisplayResults(ItemName, ItemList)); %>

这不是完整的代码，但它是解决我在问题中解决的问题所需的代码。通过这种方式加载用户控件，我们可以设置所需的属性并显示带有正确信息的 uesr 控件。

While Justin Grant's answer would likely hav worked just fine, we decided to go with just loading the user control and calling the DisplayResults method.

<% ((UserControlType)LoadControl("~/pathToUserControl.ascx"))
       .DisplayResults(ItemName, ItemList)); %>

That is not the complete code, but it is what was needed to solve the issue I addressed in the question. By loading the user control this way, we could set the properties we needed and display the uesr control with the correct information.

回复收藏 0 原文

~没有更多了~