从通用列表中将ListItem添加到DropDownList [英] Adding ListItems to a DropDownList from a generic list

问题描述

我有一个这个aspx代码：（sample）

I have a this aspx-code: (sample)

<asp:DropDownList runat="server" ID="ddList1"></asp:DropDownList>   

使用此codebehind：

With this codebehind:

List<System.Web.UI.WebControls.ListItem> colors = new List<System.Web.UI.WebControls.ListItem>();
colors.Add(new ListItem("Select Value", "0"));
colors.Add(new ListItem("Red", "1"));
colors.Add(new ListItem("Green", "2"));
colors.Add(new ListItem("Blue", "3"));
ddList1.DataSource = colors;
ddList1.DataBind();

输出如下所示：

<select name="ddList1" id="ddList1">
    <option value="Select Value">Select Value</option>
    <option value="Red">Red</option>
    <option value="Green">Green</option>
    <option value="Blue">Blue</option>
</select>   

我的问题是：为什么我的值（数字）消失，文本用作值AND文本？我知道如果我使用 ddList1.Items.Add（New ListItem（text，value））方法，但我需要使用通用列表作为数据源的其他原因。

My question is: Why did my values (numbers) disappear and the text used as the value AND the text? I know that it works if I use the ddList1.Items.Add(New ListItem("text", "value")) method, but I need to use a generic list as the datasource for other reasons.

推荐答案

因为DataBind方法只有在DataValueField属性设置时才绑定值。如果在调用DataBind之前将DataValueField属性设置为Value，您的值将显示在标记上。

Because DataBind method binds values only if DataValueField property is set. If you set DataValueField property to "Value" before calling DataBind, your values will appear on the markup.

更新：您还需要将DataTextField属性设置为Text 。这是因为手动的数据绑定和添加项不能以同样的方式工作。数据绑定不知道类型ListItem的存在，并通过评估数据源中的项来生成标记。

UPDATE: You will also need to set DataTextField property to "Text". It is because data binding and adding items manually do not work in the same way. Databinding does not know the existence of type ListItem and generates markup by evaluating the items in the data source.

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