WPF组合框值和显示文本

Question

我习惯这样做

State.Items.Add(new ListItem { Text = "SomeState", Value = NumericIDofState });

State是ASP.NET中的列表框.

我如何使用WPF ComboBox实现相同的目标？我确实在ComboBoxItem对象中看到了一个名为"Content"的属性,但是如何为每个项目分配一个值而不是显示给用户的值？请帮忙.

Answer 1

WPF Combobox有:

• SelectedValuePathproperty,指定用于确定SelectedValue 属性值的属性的路径.它类似于ASP.NET ListItem的Value属性.
• DisplayMemberPath定义描述如何显示数据对象的默认模板的属性.它类似于ASP.NET ListItem的Text属性.

假设您希望Combobox显示以下KeyValuePair对象的集合:

private static readonly KeyValuePair<int, string>[] tripLengthList = {
    new KeyValuePair<int, string>(0, "0"),
    new KeyValuePair<int, string>(30, "30"), 
    new KeyValuePair<int, string>(50, "50"), 
    new KeyValuePair<int, string>(100, "100"), 
};

您在视图模型中定义一个返回该集合的属性:

public KeyValuePair<int, string>[] TripLengthList
{
    get
    {
        return tripLengthList;
    }
}

然后,您的XAML Combobox将是:

<ComboBox
    SelectedValue="{Binding FilterService.TripLengthFrom, Mode=TwoWay}"
    ItemsSource="{Binding TripLengthList, Mode=OneTime}"
    SelectedValuePath="Key"
    DisplayMemberPath="Value" />

在哪里设置SelectedValuePath和DisplayMemberPath属性为对象的所需属性名称(Key并Value相应地)由显示Combobox.

或者,如果您真的想要Combobox在代码后面添加项而不是使用绑定,那么您也可以这样做.例如:

<!--XAML-->
<ComboBox x:Name="ComboBoxFrom"
    SelectedValue="{Binding FilterService.TripLengthFrom, Mode=TwoWay}" />

// Code behind
public partial class FilterView : UserControl
{
    public FilterView()
    {
        this.InitializeComponent();

        this.ComboBoxFrom.SelectedValuePath = "Key";
        this.ComboBoxFrom.DisplayMemberPath = "Value";
        this.ComboBoxFrom.Items.Add(new KeyValuePair<int, string>(0, "0"));
        this.ComboBoxFrom.Items.Add(new KeyValuePair<int, string>(30, "30"));
        this.ComboBoxFrom.Items.Add(new KeyValuePair<int, string>(50, "50"));
        this.ComboBoxFrom.Items.Add(new KeyValuePair<int, string>(100, "100"));
    }

Answer 2

如果您只想在viewmodel中公开一个简单的属性并处理视图中选项的文本,您可以执行如下简单的解决方案:

    <ComboBox SelectedValuePath="Tag" SelectedValue="{Binding YourIntProperty, Mode=TwoWay}">
        <ComboBoxItem Content="First choice" Tag="0"/>
        <ComboBoxItem Content="Second choice" Tag="1"/>
        <ComboBoxItem Content="Third choice" Tag="2"/>
    </ComboBox>

bool属性的示例:

    <ComboBox SelectedValuePath="Tag" SelectedValue="{Binding IsActive, Mode=TwoWay}">
        <ComboBoxItem Content="No" Tag="False"/>
        <ComboBoxItem Content="Yes" Tag="True"/>
    </ComboBox>

类型 - 详细替代(原始示例)

下面是明确声明类型的更详细的替代方案.根据您的喜好风格(或某些需要它的类型),也许它更适合您.

<ComboBox SelectedValuePath="Tag" SelectedValue="{Binding YourIntProperty, Mode=TwoWay}">
    <ComboBoxItem Content="First choice">
        <ComboBoxItem.Tag>
            <sys:Int32>0</sys:Int32>
        </ComboBoxItem.Tag>
    </ComboBoxItem>
    <ComboBoxItem Content="Second choice">
        <ComboBoxItem.Tag>
            <sys:Int32>1</sys:Int32>
        </ComboBoxItem.Tag>
    </ComboBoxItem>
    <ComboBoxItem Content="Third choice">
        <ComboBoxItem.Tag>
            <sys:Int32>2</sys:Int32>
        </ComboBoxItem.Tag>
    </ComboBoxItem>
</ComboBox>

bool属性的示例:

<ComboBox SelectedValuePath="Tag" SelectedValue="{Binding IsActive, Mode=TwoWay}">
    <ComboBoxItem Content="No">
        <ComboBoxItem.Tag>
            <sys:Boolean>False</sys:Boolean>
        </ComboBoxItem.Tag>
    </ComboBoxItem>
    <ComboBoxItem Content="Yes">
        <ComboBoxItem.Tag>
            <sys:Boolean>True</sys:Boolean>
        </ComboBoxItem.Tag>
    </ComboBoxItem>
</ComboBox>

sys命名空间声明为:

xmlns:sys="clr-namespace:System;assembly=mscorlib"

Answer 3

请参阅组合的这些属性:

• 的DisplayMemberPath
• SelectedValuePath