使用ItemsSource和使用组合框之前，WPF Items集合必须为空 [英] WPF Items collection must be empty before using ItemsSource and help using Combo Box

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本文介绍了使用ItemsSource和使用组合框之前，WPF Items集合必须为空的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="1.5*"/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>  



    <Grid Grid.Column="0" Background="DarkCyan">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>    
            <ComboBox ItemsSource="{Binding Path=charList}" x:Name="comboBox" VerticalAlignment="Top" Width="Auto" Grid.ColumnSpan="2">
            <ComboBoxItem>
                <StackPanel Orientation="Horizontal">
                    <Image Source="Pictures\bagi_warrior.jpg" Width="100" Height="150"/>
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition/>
                            <RowDefinition Height="6*"/>
                        </Grid.RowDefinitions>
                        <Label Grid.Row="0" Content="{Binding Path=Character.Name}" FontSize="30"/>
                        <Label Grid.Row="1" Content="{Binding Path=Character.Level}" FontSize="20"/>
                    </Grid>
                </StackPanel>
            </ComboBoxItem>
            <ComboBoxItem>
                <StackPanel Orientation="Horizontal">
                    <Image Source="Pictures\azure_knight.jpg" Width="100" Height="130"/>
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition/>
                            <RowDefinition Height="6*"/>
                        </Grid.RowDefinitions>
                        <Label Grid.Row="0" Content="Azure Knight"  FontSize="30"/>
                        <Label Grid.Row="1" Content="Level 158"  FontSize="20"/>
                    </Grid>
                </StackPanel>
            </ComboBoxItem>
        </ComboBox>
        <Label x:Name="strLabel" Grid.Column="0" VerticalAlignment="Bottom" Height="30" Content="Str: " HorizontalContentAlignment="Center" FontSize="16"/>
        <Label x:Name="intLabel" Grid.Column="1" VerticalAlignment="Bottom" Height="30" Content="Int: " HorizontalContentAlignment="Center" FontSize="16"/>
        <Label x:Name="dexLabel" Grid.Column="0" Grid.Row="1" VerticalAlignment="Center" Height="30" Content="Dex: " HorizontalContentAlignment="Center" FontSize="16"/>
        <Label x:Name="goldLabel" Grid.Column="1" Grid.Row="1" VerticalAlignment="Center" Height="30" Content="Gold: " HorizontalContentAlignment="Center" FontSize="16"/>


    </Grid>
    <Grid Grid.Column="1">
        <Grid.RowDefinitions>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <DataGrid x:Name="MyGrid" ItemsSource="{Binding Path=Item}"></DataGrid>
    </Grid>
</Grid>

我的XAML是这样，看起来像这样：

My XAML is such, it looks like this:

http://puu.sh/aLLrx.png

http://puu.sh/aLLsQ.jpg

我的代码是：

 public partial class MainWindow : Window
 {

    Character aloken;
    Character azureKnight;
    Character bagiWarrior;
    Character incarMagician;
    Character segitaHunter;
    Character segnale;
    Character viciousSummoner;
    private List<Character> _charList = new List<Character>();

    public MainWindow()
    {
        InitializeComponent();
        charList.Add(new Character("Bagi Warrior"));
        this.Item = new ObservableCollection<Item>();
        this.Character = new ObservableCollection<Character>();

        this.DataContext = this;
        //Character.Add(new Character(name: "Bagi Warrior", level: 197, characterClass: CharacterClass.Bagi_Warrior, gender: Gender.Male, strength: 450, intelligence: 4, dexterity: 84, gold: 147203352));
        //Character.Add(new Character(name: "Azure Knight", level: 158, characterClass: CharacterClass.Azure_Knight, gender: Gender.Male, strength: 390, intelligence: 120, dexterity: 92, gold: 204220567));
        //Character.Add(new Character(name: "Incar Magician", level: 169, characterClass: CharacterClass.Incar_Magician, gender: Gender.Female, strength: 4, intelligence: 512, dexterity: 57, gold: 172223520));
        //Character.Add(new Character(name: "Vicious Summoner", level: 203, characterClass: CharacterClass.Vicious_Summoner, gender: Gender.Male, strength: 423, intelligence: 89, dexterity: 45, gold: 114225587));

    }

    public List<Character> charList
    {
        get { return _charList; }
        set { _charList = value; }
    }


    private ObservableCollection<Character> _Character;

    public ObservableCollection<Character> Character
    {
        get { return _Character; }
        set { _Character = value; }
    }


    private ObservableCollection<Item> _Item;
    public ObservableCollection<Item> Item
    {
        get { return _Item; }
        set { _Item = value; }
    }

}

字符类（以防万一）：
http://pastebin.com/GFycKqDC

Character Class (just in case): http://pastebin.com/GFycKqDC

商品类（以防万一）：
http://pastebin.com/RgXzbFHk

Item Class (just in case): http://pastebin.com/RgXzbFHk

这是RPG上的一个项目，在该项目中，您必须对组合框使用数据绑定，并为组合框创建ObservableCollection并查看每个角色。

It's a project on a RPG where you have to use databinding for a combobox and to create an ObservableCollection for the combobox and view each Character.

我遇到的问题是：
在我的组合框中，我希望能够显示角色及其图像，并在其旁边显示其水平和'name'

The issue i'm running into is: In my combobox, I want to be able to display the Character with their 'image' and next to it, their 'level' and 'name'

但是我不希望它是静态的，我想创建一个字符列表并将ItemsSource绑定到我的ComboBox以便无论哪个字符我选择，基于该字符的信息将更新。
我该怎么做？

But I don't want it to be static, I want to create a list of Characters and bind the ItemsSource to my ComboBox so that no matter which character I select, information based on that character will update. How do I do this?

有人告诉我创建一个字符列表，然后为ComboBox Item创建一个数据模板，其中包含图片，名称，绑定到selectedItem的层和级别都可以完成这项工作（我确实将其称为charList），但是无论我是在代码中还是在XAML中进行操作，它都会引发异常，指出在绑定到该集合之前，该集合必须为空。

I was told that creating a List of Characters, then make a data template for ComboBox Item that holds a pic, name, and level that are bound to selectedItem would do the job (which I did called charList) but whether I do it in code, or in XAML, it throws an exception saying that the collection must be empty before I bind to it.

我想将数据模板中的属性绑定到selectedItem，以便标签和信息会适当更新。

I want to bind the properties in the datatemplate to selectedItem so that the labels and information will update appropriately.

什么是我做错了，为什么会抛出此异常？

What am I doing wrong, and why is this exception being thrown?

EDIT
























EDIT

好，现在问题已解决！但是，为什么我的Label绑定仍然不能用于Character.Name和Character.Level？

Okay so now the problem is fixed! However, why does my Label binding still not work for Character.Name and Character.Level?

http://puu.sh/aLPr7.jpg

编辑2
公共MainWindow（）
{
InitializeComponent（）;
Character.Add（new Character（ Bagi Warrior））;
Character.Add（new Character（ Azure Knight））;
this.Item = new ObservableCollection（）;
this.Character = new ObservableCollection（）;

EDIT 2 public MainWindow() { InitializeComponent(); Character.Add(new Character("Bagi Warrior")); Character.Add(new Character("Azure Knight")); this.Item = new ObservableCollection(); this.Character = new ObservableCollection();

        this.DataContext = this;
        //Character.Add(new Character(name: "Bagi Warrior", level: 197, characterClass: CharacterClass.Bagi_Warrior, gender: Gender.Male, strength: 450, intelligence: 4, dexterity: 84, gold: 147203352));
        //Character.Add(new Character(name: "Azure Knight", level: 158, characterClass: CharacterClass.Azure_Knight, gender: Gender.Male, strength: 390, intelligence: 120, dexterity: 92, gold: 204220567));
        //Character.Add(new Character(name: "Incar Magician", level: 169, characterClass: CharacterClass.Incar_Magician, gender: Gender.Female, strength: 4, intelligence: 512, dexterity: 57, gold: 172223520));
        //Character.Add(new Character(name: "Vicious Summoner", level: 203, characterClass: CharacterClass.Vicious_Summoner, gender: Gender.Male, strength: 423, intelligence: 89, dexterity: 45, gold: 114225587));

    }

    //public List<Character> charList
    //{
    //    get { return _charList; }
    //    set { _charList = value; }
    //}


    private ObservableCollection<Character> _Character;

    public ObservableCollection<Character> Character
    {
        get { return _Character; }
        set { _Character = value; }
    }

然后是XAML：

<Grid Grid.Column="0" Background="DarkCyan">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <ComboBox ItemsSource="{Binding Path=Character}" x:Name="comboBox" VerticalAlignment="Top" Width="Auto" Grid.ColumnSpan="2">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <Image x:Name="image" Source="{Binding Source={StaticResource ImageConverter}}" Width="100" Height="150"/>
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition/>
                                <RowDefinition Height="6*"/>
                            </Grid.RowDefinitions>
                            <Label Grid.Row="0" Content="{Binding Path=Character.Name}" FontSize="30"/>
                            <Label Grid.Row="1" Content="{Binding Path=Character.Level}" FontSize="20"/>
                        </Grid>
                    </StackPanel>
                </DataTemplate>
            </ComboBox.ItemTemplate>


推荐答案

您两次定义了ItemsSource。

You are defining the ItemsSource twice.

一次使用

ItemsSource="{Binding charList}"

然后再次使用

<ComboBoxItem>

您将要替换 ComboBoxItem 元素与 ComboBox.ItemTemplate 并为您的 ComboxItem 创建 DataTemplate 。然后，您需要将图像源绑定到Character类上的属性，或使用 ItemTemplateSelector 使其使用适当的 DataTemplate 。
如果仅更改图像源位置，则还可以使用绑定到定义字符类的属性的数据触发器。

You will want to replace the ComboBoxItem element with ComboBox.ItemTemplate and create a DataTemplate for your ComboxItem. Then you'll want to either bind the Image Source to a property on the Character class or use a ItemTemplateSelector to have it use the appropriate DataTemplate for the item. If only the image source location is changing, you could also use a datatrigger bound to the property defining the character class.

这篇关于使用ItemsSource和使用组合框之前，WPF Items集合必须为空的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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