Question

如何在我的UWP App中为ComboBox定义自定义模板，对于Dropdown我需要一个带标签的复选框，但是当用户选择任何选项时我只需要在comobox中显示标签

我尝试了这个，但我没有工作：

 <ComboBox x:Name="cbCountry"
                      Header="Country"
                      Margin="10,5"
                      HorizontalAlignment="Stretch"
                      Style="{StaticResource ComboBoxStyle}">
                <ComboBox.ItemTemplate>
                    <DataTemplate>
                        <CheckBox Content="{Binding}"></CheckBox>
                    </DataTemplate>
                </ComboBox.ItemTemplate>
                <ComboBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <TextBlock Text="{Binding}"/>
                    </ItemsPanelTemplate>
                </ComboBox.ItemsPanel>

Answer 1

<Page.Resources>
        <local:BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"/>
</Page.Resources>
 <ComboBox x:Name="cbState" DropDownClosed="cbState_DropDownClosed" DropDownOpened="cbState_DropDownOpened"  Margin="75,287,0,0" Width="169" ItemContainerStyle="{StaticResource ComboBoxItemStyle1}" Style="{StaticResource ComboBoxStyle1}"   >

                <ComboBox.ItemTemplate>
                    <DataTemplate>
                    <StackPanel>
                        <CheckBox Content="{Binding}" 
                                   Visibility="{Binding IsCheckBoxVisible, Mode=TwoWay, Converter={StaticResource BooleanToVisibilityConverter}, UpdateSourceTrigger=PropertyChanged}" >
                            </CheckBox>
                        <TextBlock Text="{Binding State_Name}"/>
                    </StackPanel>
                </DataTemplate>
                </ComboBox.ItemTemplate>

            </ComboBox>

   private void cbState_DropDownClosed(object sender, object e)
        {
            foreach (var item in (sender as ComboBox).Items)
            {
                (item as State).IsCheckBoxVisible = false;
            }
        }

        private void cbState_DropDownOpened(object sender, object e)
        {
            foreach(var item in (sender as ComboBox).Items)
            {
                (item as State).IsCheckBoxVisible = true;
            }
        }

转换器类

 public class BooleanToVisibilityConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, string language)
        {
            var boolValue = System.Convert.ToBoolean(value);

            return boolValue ? Visibility.Visible : Visibility.Collapsed;
        }

        public object ConvertBack(object value, Type targetType, object parameter, string language)
        {
            return ((Visibility)value == Visibility.Visible) ? true : false;
            ;
        }
    }

模型类。实现INotifyPropertyChanged以反映UI中的更改（复选框可见性更改）

 public class State:INotifyPropertyChanged
    {
        public string State_Name { get; set; }
        public object State_Id { get; set; }
        bool isCheckBoxVisible;
        public bool IsCheckBoxVisible
        {
            get { return isCheckBoxVisible; }
            set
            {
                if (value != isCheckBoxVisible)
                {
                    isCheckBoxVisible = value;
                    OnPropertyChanged("IsCheckBoxVisible");
                }
            }
        }
        public State(string name,object id,bool visibility=false)
        {
            State_Name = name;
            State_Id = id;
            IsCheckBoxVisible = false;
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public override string ToString()
        {
            return State_Name;
        }
        void OnPropertyChanged(string propertyName)
        {
            // the new Null-conditional Operators are thread-safe:
            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

    }

如何为下拉列表创建不同的ComboBox ItemTemplate

1 个答案: