无法转换为基类

Question

我正在构建一个带有组合框和数据网格的 wpf 表单。组合框绑定到模型基类 moWeek 的集合。所选项目绑定到一个名为 wm 的派生类，例如 SelectedItem="{Binding Week, Mode=TwoWay}"，而只是 Viewmodel 类中 vm 类型的属性。

现在，当我从组合框中选择一个值时，我得到一个名为 TypeConverter 的 System.NotSupportedException 无法转换 model.moWeek。

我想我需要某种从 moWeek 到 vmWeek 的转换器，但我不知道在哪里以及如何放置它。我该怎么做？

代码如下：

模特周班：

using System.Collections.ObjectModel;

namespace Model
{
    public class moWeek
    {

        public moWeek()
        {

        }

        private int id;

        public int Id
        {
            get { return id; }
            set { id = value; }
        }
    }
}

Viewmodel 周课：

using System;
using System.ComponentModel;
using Model;
using ViewModel.Lists;

namespace ViewModel.Planning
{
    public class vmWeek  : moWeek
    {
        private ProjectList projects;

        public ProjectList Projects
        {
            get { return projects; }
            set { projects = value; OnPropertyChanged(new PropertyChangedEventArgs("Projects")); }
        }

        private void OnPropertyChanged(PropertyChangedEventArgs propertyChangedEventArgs)
        {
            throw new NotImplementedException();
        }
    }
}

视图模型

using System.ComponentModel;
using tegViewModel.Auswahllisten;


namespace tegViewModel.Planning
{
    public class vmPlanning : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public vmPlanning()
        {
            Weeks = new alWeeks(); //Collection of moWeek

        }

        public alWeeks Weeks { get; set; }

        private vmWeek week;

        public vmWeek Week
        {
            get { return Week; }
            set { Week = value; OnPropertyChanged(new PropertyChangedEventArgs("Week")); }
        }


        private void OnPropertyChanged(PropertyChangedEventArgs propertyChangedEventArgs)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyChangedEventArgs.PropertyName));
            }

        }
    }
}

Answer 1

首先你需要创建一个实现接口IValueConverter的类

[ValueConversion(typeof(moWeek), typeof(vmWeek))]
class MoWeekToVmWeekConverter: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var moweek = value as moWeek;
        vmWeek result = //Do your conversion;
        return result;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (moWeek) value;
    }
}

之后，您可以在资源中声明该类的实例。

<local:MoWeekToVmWeekConverter x:Key="MoWeekConverter"></local:MoWeekToVmWeekConverter>

一旦你声明了转换器，你就可以在绑定中使用它。

<ComboBox SelectedItem="{Binding Week, Mode=TwoWay, Converter={StaticResource MoWeekConverter}}"></ComboBox>