ASP.Net：ListView 的 ItemTemplate 中的条件逻辑

发布于 2024-07-26 02:13:28 字数 784 浏览 3 评论 0原文

我想根据绑定字段是否为空来显示 ItemTemplate 的某些部分。以下面的代码为例：

（为简洁起见，已删除诸如 LayoutTemplate 之类的代码）

<asp:ListView ID="MusicList" runat="server">
    <ItemTemplate>
        <tr>
            <%
                if (Eval("DownloadLink") != null)
                {
            %>
            <td>
                <a href="<%#Eval("DownloadLink") %>">Link</a>
            </td>
            <%
                } %>
        </tr>
    </ItemTemplate>
</asp:ListView>

上面给出了以下运行时错误：

数据绑定方法，例如 Eval()、只能使用 XPath() 和 Bind() 在数据绑定控件的上下文中。

那么如何将一些条件逻辑（如上面的）放入 ItemTemplate 中？

原文

I want to show certain parts of an ItemTemplate based according to whether a bound field is null. Take for example the following code:

(Code such as LayoutTemplate have been removed for brevity)

<asp:ListView ID="MusicList" runat="server">
    <ItemTemplate>
        <tr>
            <%
                if (Eval("DownloadLink") != null)
                {
            %>
            <td>
                <a href="<%#Eval("DownloadLink") %>">Link</a>
            </td>
            <%
                } %>
        </tr>
    </ItemTemplate>
</asp:ListView>

The above gives the following run-time error:

Databinding methods such as Eval(),
XPath(), and Bind() can only be used
in the context of a databound control.

So how can put some conditional logic (like the above) in an ItemTemplate ?

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唱一曲作罢 2024-08-02 02:13:28

将控件的“Visible”属性绑定到您的条件怎么样？就像是：

<asp:ListView ID="MusicList" runat="server">
   <ItemTemplate>
    <tr runat="server" Visible='<%# Eval("DownloadLink") != null %>'>
        <td>
            <a href='<%#Eval("DownloadLink") %>'>Link</a>
        </td>
    </tr>
   </ItemTemplate>
</asp:ListView>

What about binding the "Visible" property of a control to your condition? Something like:

<asp:ListView ID="MusicList" runat="server">
   <ItemTemplate>
    <tr runat="server" Visible='<%# Eval("DownloadLink") != null %>'>
        <td>
            <a href='<%#Eval("DownloadLink") %>'>Link</a>
        </td>
    </tr>
   </ItemTemplate>
</asp:ListView>

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弥枳 2024-08-02 02:13:28

解决“服务器标记格式不正确”的问题。对于涉及可见性的答案，请删除 Visible= 参数中的引号。

所以它会变成：

<tr runat="server" Visible=<%# Eval("DownloadLink") != null ? true : false %>>

To resolve "The server tag is not well formed." for the answers involving visibility, remove quotes from the Visible= parameter.

So it will become:

<tr runat="server" Visible=<%# Eval("DownloadLink") != null ? true : false %>>

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み格子的夏天 2024-08-02 02:13:28

我不建议将此作为一个好方法，但您可以通过捕获 OnItemDataBound 事件中的当前项目，将其存储在公共属性或字段中，然后在条件逻辑中使用它来解决此问题。

例如：

<asp:ListView ID="MusicList" OnItemDataBound="Item_DataBound" runat="server">
    <ItemTemplate>
        <tr>
            <%
                if (CurrentItem.DownloadLink != null)
                {
            %>
            <td>
                <a href="<%#Eval("DownloadLink") %>">Link</a>
            </td>
            <%
                } %>
        </tr>
    </ItemTemplate>
</asp:ListView>

在服务器端将以下代码添加到代码隐藏文件中：

public MusicItem CurrentItem { get; private set;}

protected void Item_DataBound(object sender, RepeaterItemEventArgs e)
{
   CurrentItem = (MusicItem) e.Item.DataItem;
}

请注意，此技巧在 UpdatePanel 控件中不起作用。

I'm not recommending this as a good approach but you can work around this issue by capturing the current item in the OnItemDataBound event, storing it in a public property or field and then using that in your conditional logic.

For example:

<asp:ListView ID="MusicList" OnItemDataBound="Item_DataBound" runat="server">
    <ItemTemplate>
        <tr>
            <%
                if (CurrentItem.DownloadLink != null)
                {
            %>
            <td>
                <a href="<%#Eval("DownloadLink") %>">Link</a>
            </td>
            <%
                } %>
        </tr>
    </ItemTemplate>
</asp:ListView>

And on the server side add the following code to your code behind file:

public MusicItem CurrentItem { get; private set;}

protected void Item_DataBound(object sender, RepeaterItemEventArgs e)
{
   CurrentItem = (MusicItem) e.Item.DataItem;
}

Note that this trick will not work in an UpdatePanel control.

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酒解孤独 2024-08-02 02:13:28

如果您有 2 个不同的结构要根据条件渲染，则使用面板

<asp:ListView ID="MusicList" runat="server">
    <ItemTemplate>
        <tr>
            <asp:Panel ID="DownloadNull" runat="server" Visible="<%# Eval("DownloadLink") == null %>" >
            <td> Album Description BlaBlaBla <img src="../images/test.gif"> </td>
            </asp:Panel>

            <asp:Panel ID="DownloadNotNull" runat="server" Visible="<%# Eval("DownloadLink") != null %>" >
            <td> Album Description BlaBlaBla <img src="../images/test.gif">
                <a href='<%# Eval("DownloadLink")' >Download</a>
                ..... 
            </td>
            </asp:Panel>
        </tr>
    </ItemTemplate>
</asp:ListView>

If you have 2 different structure that are to be rendered according to a condition then use panels

<asp:ListView ID="MusicList" runat="server">
    <ItemTemplate>
        <tr>
            <asp:Panel ID="DownloadNull" runat="server" Visible="<%# Eval("DownloadLink") == null %>" >
            <td> Album Description BlaBlaBla <img src="../images/test.gif"> </td>
            </asp:Panel>

            <asp:Panel ID="DownloadNotNull" runat="server" Visible="<%# Eval("DownloadLink") != null %>" >
            <td> Album Description BlaBlaBla <img src="../images/test.gif">
                <a href='<%# Eval("DownloadLink")' >Download</a>
                ..... 
            </td>
            </asp:Panel>
        </tr>
    </ItemTemplate>
</asp:ListView>

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