Question

我有“在使用ItemsSource之前，项目集合必须为空。”我的代码出错

我在StackOverFlow链接中测试所有答案但是他们没有工作！我的Xaml：

<Window x:Class="FirstWpfTestApplication.Main"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:FirstWpfTestApplication"
    xmlns:valConverter="clr-namespace:FirstWpfTestApplication.Model.ValueConverters"
    mc:Ignorable="d"
    Title="Main" Height="500" Width="800" WindowStartupLocation="CenterScreen">
<UserControl>
    <UserControl.Resources>
        <valConverter:GenderConverter x:Key="GenderConverter"/>
        <valConverter:EnumList x:Key="EnumConverter"/>
        <Style TargetType="TextBox">
            <Setter Property="MinWidth" Value="100"/>
            <Setter Property="Margin" Value="5"/>
        </Style>
        <Style TargetType="TextBlock">
            <Setter Property="Margin" Value="5"/>
        </Style>
        <Style TargetType="RadioButton">
            <Setter Property="Margin" Value="5"/>
        </Style>
        <Style TargetType="CheckBox">
            <Setter Property="Margin" Value="5"/>
        </Style>
        <Style TargetType="ComboBox">
            <Setter Property="MinWidth" Value="100"/>
        </Style>
        <Style TargetType="Button">
            <Setter Property="Margin" Value="5"/>
            <Setter Property="MinWidth" Value="60"/>
        </Style>
    </UserControl.Resources>
    <Grid>
        <DockPanel>
            <!--<ListBox Name="lstPeople" DockPanel.Dock="Left">
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <TextBlock Text="Name:" Margin="10 0"/>
                        <TextBlock Text="{Binding Name}" Margin="10 0"/>
                    </StackPanel>
                </DataTemplate>
            </ListBox>-->
            <Border BorderThickness="2" BorderBrush="Black" CornerRadius="1">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="auto"/>
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="auto"/>
                        <RowDefinition Height="auto"/>
                        <RowDefinition Height="auto"/>
                        <RowDefinition Height="auto"/>
                        <RowDefinition Height="auto"/>
                    </Grid.RowDefinitions>
                    <StackPanel Orientation="Horizontal" Grid.Column="0" Grid.Row="0" Margin="10">
                        <TextBlock>Name:</TextBlock>
                        <TextBox Text="{Binding Name}"></TextBox>
                    </StackPanel>
                    <StackPanel Orientation="Horizontal" Grid.Column="0" Grid.Row="1" Margin="10">
                        <TextBlock VerticalAlignment="Center">Gender:</TextBlock>
                        <WrapPanel Orientation="Vertical">
                            <RadioButton IsChecked="{Binding Gender,Converter={StaticResource GenderConverter},ConverterParameter=True}"
                            Name="rdMan">
                                Man
                            </RadioButton>
                            <RadioButton IsChecked="{Binding Gender,Converter={StaticResource GenderConverter},ConverterParameter=False}"
                             Name="rdWoman">
                                WoMan
                            </RadioButton>
                        </WrapPanel>
                    </StackPanel>
                    <StackPanel Orientation="Horizontal" Grid.Column="0" Grid.Row="2" Margin="10">
                        <TextBlock>Field Of Work:</TextBlock>
                        <StackPanel Orientation="Horizontal">
                            <CheckBox Name="chActor" IsChecked="{Binding FieldOfWorks,Converter={StaticResource EnumConverter},ConverterParameter=Actor}">
                                Actor
                            </CheckBox>
                            <CheckBox Name="chDirector" IsChecked="{Binding FieldOfWorks,Converter={StaticResource EnumConverter},ConverterParameter=Director}">
                                Director
                            </CheckBox>
                            <CheckBox Name="chProducer" IsChecked="{Binding FieldOfWorks,Converter={StaticResource EnumConverter},ConverterParameter=Producer}">
                                Producer
                            </CheckBox>
                        </StackPanel>
                    </StackPanel>
                    <StackPanel Grid.Row="3" Orientation="Horizontal">
                        <TextBlock>Country:</TextBlock>
                        <ComboBox Name="cbCountries">
                            <DataTemplate>
                                <TextBlock Text="{Binding Name}"/>
                            </DataTemplate>
                        </ComboBox>
                    </StackPanel>
                    <StackPanel Margin="0 10" HorizontalAlignment="Left" Orientation="Horizontal" Grid.Row="4">
                        <Button>Save</Button>
                    </StackPanel>
                </Grid>
            </Border>
        </DockPanel>
    </Grid>
</UserControl>

和我的C＃代码：

    public partial class Main : Window
{
    public List<People> PeopleContext;        
    public Main()
    {
        InitializeComponent();

        this.DataContext = People.GetPeople();
        cbCountries.ItemsSource = new Country().GetCountries();//In This Line Exception Will Throw


    }
}

请帮助解决WPF中的此问题

Answer 1

你的组合框直接使用DataTemplate。而是放在ItemTemplate属性中。请参阅下面的代码。

 <ComboBox Name="cbCountries">
                    <ComboBox.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding Name}"/>
                        </DataTemplate>
                    </ComboBox.ItemTemplate>
                </ComboBox>

在使用ItemsSource之前，项集合必须为空。

1 个答案: