WPF綁定DataGridComboBoxColumn的SelectedItemBinding

Question

我有一個學生班，定義了學生的屬性，如下所示

 public class Student
    {
        public string Department { get; set; }

    public string Level { get; set; }

    public Gender Gender { get; set; }

    public string Nationality { get; set; }

}

我還有另一個類，其中包含聲明的集合中的國家/地區列表，如下所示

public class Countries
    {
 public static ObservableCollection<string> Nationalities { get; } = new ObservableCollection<string>()
        {
            "Afghanistan",
            "Albania",
            "Algeria",
            "Andorra",
            "Angola",
            "Anguilla",
            "Antigua & Barbuda",
            "Argentina",
            "Armenia",
            "Australia",
            "Austria",
            "Azerbaijan",
            "Bahamas",
            "Bahrain",
            "Bangladesh",
            "Barbados",
            "Belarus",
            "Belgium",
            "Belize",
            "Benin",
            "Bermuda",
            "Bhutan",
            "Bolivia",
            "Bosnia & Herzegovina",
            "Botswana",
            "Brazil",
}

在我的視圖模型中，我聲明了一個可觀察的集合，該集合已初始化為國家/地區列表。 這是在視圖模型的構造函數內部完成的，如下所示

public class ViewModel : BaseViewModel
    {
     public ObservableCollection<string> Nationalities { get; private set; }
         public ViewModel()
        {

            // Set the nationality list
            Nationalities = Countries.Nationalities;

        }
}

現在，我像這樣創建了DataGridComboBoxColumn，

 <DataGrid.Columns>
                        <DataGridComboBoxColumn Width="Auto"
                                                    SelectedItemBinding="{Binding Path=Student.Nationality}"
                                                    Header="Nationality" 
                                                    x:Name="NationalityComboBox2">
                            <DataGridComboBoxColumn.EditingElementStyle>
                                <Style TargetType="ComboBox">
                                    <Setter Property="ItemsSource" Value="{Binding Path=DataContext.Nationalities, ElementName=StudentListGrid}" />
                                </Style>
                            </DataGridComboBoxColumn.EditingElementStyle>
                        </DataGridComboBoxColumn>
                    </DataGrid.Columns>

當我運行我的應用程序時，DataGridComboBoxColumn包含所有國家/地區，但是當我選擇一個特定國家/地區時，不會顯示該信息。我在網上看到了類似的問題，但沒有看到任何適合我的情況的答案。 有什么建議么？

Answer 1

除了使用DataGridComboBoxColumn，還可以使用DataGridTemplateColumn來實現相同的目的。 您可能必須編寫一些代碼來維護文本框和comboBox的樣式。

 <DataGridTemplateColumn  Header="Nationality" >
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding Nationality}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
                <DataGridTemplateColumn.CellEditingTemplate>
                    <DataTemplate>
                        <ComboBox SelectedItem="{Binding Nationality}" ItemsSource="{Binding Path=DataContext.Nationalities, ElementName=StudentListGrid}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellEditingTemplate>
            </DataGridTemplateColumn>

Answer 2

我認為您需要在Student上實現INotifyPropertyChanged接口

public class Student : INotifyPropertyChanged
{

    public event PropertyChangedEventHandler PropertyChanged;

    public string Department { get; set; }

    public string Level { get; set; }

    public Gender Gender { get; set; }

    private string _nationality;
    public string Nationality 
    { 
        get
        {
            return _nationality;
        }  
        set
        {
            if(value != _nationality)
            {
                _nationality = value;
                OnPropertyChanged(nameof(Nationality));
            }
         } 
    }

    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
}

Answer 3

假設DataGrid的ItemsSource是IEnumerable<Student> ，則應綁定到Nationality而不是Student.Nationality ：

<DataGridComboBoxColumn Width="Auto"
                        SelectedItemBinding="{Binding Nationality}"
                        Header="Nationality" 
                        x:Name="NationalityComboBox2">
    <DataGridComboBoxColumn.EditingElementStyle>
        <Style TargetType="ComboBox">
            <Setter Property="ItemsSource" Value="{Binding Path=DataContext.Nationalities, ElementName=StudentListGrid}" />
        </Style>
    </DataGridComboBoxColumn.EditingElementStyle>
</DataGridComboBoxColumn>