从组合框中添加数据时如何检查有效选择？

Question

我的视图上有两个组合框和一个添加按钮，两个组合框都必须从中选择一个项目才能进行有效选择。

如果两个组合框都没有选择，我尝试禁用添加按钮的启用属性，但目前如果只有一个组合框被选中，按钮会重新启用。

任何人都可以针对这种情况提出修复建议，或者指出我在这个设置中哪里出了问题吗？

按钮的启用属性绑定到 ViewModel 中的属性：

 //This button enable property is bound to the combo boxes being selected  ----->
        <Button x:Name="addGradeBtn"
                Grid.Row="2"
                HorizontalAlignment="Left"
                Command="{Binding Path=AddGradeCommand}"
                Content="Add Grade"
                IsEnabled="{Binding ButtonEnabled,
                                    Mode=TwoWay}" />

        <ComboBox x:Name="subjectCmbBx"
                  Grid.Row="1"
                  Grid.ColumnSpan="2"
                  Width="199"
                  HorizontalAlignment="Left"
                  VerticalAlignment="Top"
                  DisplayMemberPath="Subject"
                  Header="Subjects"
                  ItemsSource="{Binding Subjects}"
                  PlaceholderText="Pick a subject"
                  SelectedItem="{Binding SelectedSubject,
                                         Mode=TwoWay}" />


        <ComboBox x:Name="ordinaryGradeCmbBx"
                  Grid.Row="1"
                  Grid.Column="0"
                  Grid.ColumnSpan="2"
                  Width="170"
                  HorizontalAlignment="Right"
                  DisplayMemberPath="Key"
                  Header="Grades"
                  ItemsSource="{Binding OrdinaryGradePointKV}"
                  PlaceholderText="Pick a grade"
                  SelectedValue="{Binding SelectedOrdinaryGrade,
                                          Mode=TwoWay}"
                  Visibility="{Binding IsHigher,
                                       Mode=TwoWay,
                                       Converter={StaticResource BoolToNonVisibilityConverter}}" />

        <ComboBox x:Name="higherGradeCmbBx"
                  Grid.Row="1"
                  Grid.Column="0"
                  Grid.ColumnSpan="2"
                  Width="170"
                  HorizontalAlignment="Right"
                  DisplayMemberPath="Key"
                  Header="Grades"
                  ItemsSource="{Binding HigherGradePointKV}"
                  PlaceholderText="Pick a grade"
                  SelectedValue="{Binding SelectedHigherGrade,
                                          Mode=TwoWay}"
                  Visibility="{Binding IsHigher,
                                       Mode=TwoWay,
                                       Converter={StaticResource BoolToVisibilityConverter}}" />

这是我的 ViewModel 的缩小版：

命名空间LC_Points.ViewModel { public class MainViewModel：ViewModelBase { 私人只读 IRepository _repository = App.ScoresRepository;

    public MainViewModel()
    {
        //call methods to initilise list data
        InitSubjectTypes();
        InitOrdinaryGradePairs();
        InitHigherGradePairs();
    }

    public List<ScoreModel> Subjects { get; set; }
    public List<StringKeyValue> HigherGradePointKV { get; set; }
    public List<StringKeyValue> OrdinaryGradePointKV { get; set; }

    //Button enabled binding set based on the combo boxes being selected -->
    private ScoreModel _selectedSubject;
    public ScoreModel SelectedSubject
    {
        get { return _selectedSubject; }
        set
        {
            if (value != _selectedSubject)
            {
                _selectedSubject = value;
                RaisePropertyChanged("SelectedSubject");
                //I set the buttons enabled property to true is the combo box has been selected,

但我只希望在两个组合框都被选中时启用它 ---> 按钮启用=真； } 别的 { ButtonEnabled = false; } } }

    private StringKeyValue _selectedHigherGrade;
    public StringKeyValue SelectedHigherGrade
    {
        get { return _selectedHigherGrade; }
        set
        {
            if (value != _selectedHigherGrade)
            {
                _selectedHigherGrade = value;
                RaisePropertyChanged("SelectedHigherGrade");
                ButtonEnabled = true;
            }
            else
            {
                ButtonEnabled = false;
            }
        }
    }

    private StringKeyValue _selectedOrdinaryGrade;
    public StringKeyValue SelectedOrdinaryGrade
    {
        get { return _selectedOrdinaryGrade; }
        set
        {
            if (value != _selectedOrdinaryGrade)
            {
                _selectedOrdinaryGrade = value;
                RaisePropertyChanged("SelectedOrdinaryGrade");
                ButtonEnabled = true;

            }
            else
            {
                ButtonEnabled = false;
            }
        }
    }

}

}

Answer 1

像下面这样为 Button IsEnabled 使用 MultiBinding，

  <Button.IsEnabled>
     <MultiBinding Converter="{StaticResource CheckIfBothSelectedMultiConverter}">
                <Binding Path="Combo1" />
                <Binding Path="Combo2" />
            </MultiBinding>
</Button.IsEnabled>

检查 CheckIfBothSelectedMultiConverter 转换器中的条件，如果两个值都为真 return 为真，否则为假。

public class IsEnabledCheckConverter : IMultiValueConverter
{  
    public object Convert(object[ ] values, Type targetType, object parameter, CultureInfo culture)
{
      if(Convert.ToBoolean(values[0]) && Convert.ToBoolean(values[1]))
        {
            return true;
        }
     return false;        
}

public object Convert(object[ ] values, Type targetType, object parameter, CultureInfo culture)
{
     //convert back Logic
}
}

这就是我在 Win RT/Universal App

中获得的多重绑定

 <TextBlock FontSize="20" TextWrapping="Wrap" Foreground="Cyan">
  <mb:MultiBindingLinker.Attach>
   <mb:MultiBindings>
    <mb:MultiBinding TargetProperty="Text" Converter="{StaticResource ConcatMultiConverter}">
      <mb:Binding Path="StringValue" />
      <mb:Binding Path="Text" ElementName="ConcatTextBox1"/>
      <mb:Binding Path="Text" ElementName="ConcatTextBox2" Converter="{StaticResource ToUpperCaseConverter}"/>
      <mb:Binding Path="ActualWidth" RelativeSource="{RelativeSource Self}" />
 </mb:MultiBinding>
 </mb:MultiBindings>
 </mb:MultiBindingLinker.Attach>
</TextBlock>

从组合框中添加数据时如何检查有效选择？

How to check valid selection when adding data from combo boxes?

c#

validation

binding

combobox

win-universal-app