C# 通过MVVM Light RelayCommand绑定泛型类型

我使用的隐式数据模板应用于ItemsControl的项：

<ItemsControl ItemsSource="{Binding Path=CategoryAttributeVMs}"/>

<DataTemplate DataType="{x:Type my:CategoryAttributeDateFieldVM}">
    <DockPanel>
        <.....>
        <Button Command="{Binding Path=MainViewModel.CopyToChildrenCommand,
                                  Source={StaticResource Locator}}"
                CommandParameter="{Binding Mode=OneWay}">
    </DockPanel>
</DataTemplate>

<DataTemplate DataType="{x:Type my:CategoryAttributeIntegerFieldVM}">
    <DockPanel>
        <.....>
        <Button Command="{Binding Path=MainViewModel.CopyToChildrenCommand,
                                  Source={StaticResource Locator}}"
                CommandParameter="{Binding Mode=OneWay}">
    </DockPanel>
</DataTemplate>

这是绑定到我的ViewModel的数据，如下所示：

public abstract class CategoryAttributeVM
{
    protected CategoryAttributeVM(ICategoryAttribute categoryAttribute)
    {
        _categoryAttribute = categoryAttribute;
    }

    private readonly ICategoryAttribute _categoryAttribute;

    public string Name { get { return _categoryAttribute.Name; } }
    public object Value { get { return _categoryAttribute.Value; } }
}

public abstract class CategoryAttributeVM<T> : CategoryAttributeVM
{
    protected CategoryAttributeVM(ICategoryAttribute<T> categoryAttribute)
        : base(categoryAttribute) { _categoryAttribute = categoryAttribute; }

    private readonly ICategoryAttribute<T> _categoryAttribute;

    public new T Value
    {
        get { return _categoryAttribute.Value; }
        set { _categoryAttribute.Value = value; }
    }
}

public class CategoryAttributeDateFieldVM : CategoryAttributeVM<DateTime?>
{
    public CategoryAttributeDateFieldVM(ICategoryAttributeDateField categoryAttributeDateField)
        : base(categoryAttributeDateField) { }
}

public class CategoryAttributeIntegerFieldVM: CategoryAttributeVM<Int32?>
{
    public CategoryAttributeIntegerFieldVM(ICategoryAttributeIntegerField categoryAttributeIntegerField)
       : base(categoryAttributeIntegerField) { }
}

public class MainViewModel : ViewModelBase
{
    public MainViewModel()
    {
        CategoryAttributeVMs = new List<CategoryAttributeVM>( new CategoryAttributeVM[]
            {
                new CategoryAttributeDateFieldVM(new CategoryAttributeDateField("DateField", DateTime.Now)),
                new CategoryAttributeIntegerFieldVM(new CategoryAttributeIntegerField("IntField", 123))
            });

        CategoryAttributeVM2s = new List<CategoryAttributeVM>(new CategoryAttributeVM[]
            {
                new CategoryAttributeDateFieldVM(new CategoryAttributeDateField("DateField", null)),
                new CategoryAttributeIntegerFieldVM(new CategoryAttributeIntegerField("IntField", null))
            });

        CopyToChildrenCommand = new RelayCommand<CategoryAttributeVM>(DoCopyToChildrenCommand);
    }

    public IEnumerable<CategoryAttributeVM> CategoryAttributeVMs { get; private set; }
    private IEnumerable<CategoryAttributeVM> CategoryAttributeVM2s { get; private set; }

    // This an MVVM Light RelayCommand
    public RelayCommand<CategoryAttributeVM> CopyToChildrenCommand { get; private set; }

    private void DoCopyToChildrenCommand(CategoryAttributeVM ca)
    {
        foreach (var item in CategoryAttributeVM2s)
        {
            // How to copy the ca.Value to item.Value where ca and item are of the same type?
            if (item.GetType() == ca.GetType())
                item.Value = ca.Value;  // !! No worky because item.Value refers to the CategoryAttributeVM.Value, which is a readonly Object property
        }
    }
}

公共抽象类CategoryAttributeVM
{
受保护的CategoryAttributeVM（ICategoryAttribute categoryAttribute）
{
_类别属性=类别属性；
}
私有只读ICategoryAttribute _categoryAttribute；
公共字符串名称{get{return _categoryAttribute.Name；}}
公共对象值{get{return _categoryAttribute.Value；}}
}
公共抽象类CategoryAttributeVM:CategoryAttributeVM
{
受保护的CategoryAttributeVM（ICategoryAttribute categoryAttribute）
：base（categoryAttribute）{u categoryAttribute=categoryAttribute；}
私有只读ICategoryAttribute _categoryAttribute；
公共新T值
{
获取{return\u categoryAttribute.Value；}
设置{u categoryAttribute.Value=Value；}
}
}
公共类CategoryAttributeDateFieldVM:CategoryAttributeVM
{
公共类别AttributedAteFieldVM（ICategoryAttributeDateField类别AttributedAteField）
：base（categoryAttributeDateField）{}
}
公共类CategoryAttributeFieldVM:CategoryAttributeVM
{
公共类别TributeIntegerFieldVM（ICategoryAttributeIntegerField类别TributeIntegerField）
：base（CategoryAttributeField）{}
}
公共类MainViewModel:ViewModelBase
{
公共主视图模型（）
{
CategoryAttributeVMs=新列表（新CategoryAttributeVM[]
{
新CategoryAttributeDateFieldVM（新CategoryAttributeDateField（“DateField”，DateTime.Now）），
新类别TributteIntegerFieldVM（新类别TributteIntegerField（“IntField”，123））
});
CategoryAttributeVM2s=新列表（新CategoryAttributeVM[]
{
新CategoryAttributeDateFieldVM（新CategoryAttributeDateField（“日期字段”，null）），
新类别TributteIntegerFieldVM（新类别TributteIntegerField（“IntField”，null））
});
CopyToChildrenCommand=新的RelayCommand（DoCopyToChildrenCommand）；
}
public IEnumerable CategoryAttributeVMs{get；private set；}
private IEnumerable CategoryAttributeVM2s{get；private set；}
//这是一个MVVM灯继电器命令
public RelayCommand CopyToChildrenCommand{get；private set；}
私有无效DoCopyToChildrenCommand（类别属性ca）
{
foreach（类别属性VM2S中的var项）
{
//如何将ca.Value复制到item.Value，其中ca和item的类型相同？
if（item.GetType（）==ca.GetType（））
item.Value=ca.Value；/！！没有工作，因为item.Value引用CategoryAttributeVM.Value，它是一个只读对象属性
}
}
}

如何从CategoryAttributeVM2中获取与“ca”类型匹配的对象？ 我想我遗漏了一些基本的东西，但看不见

泛型方法会很好，但是RelayCommand不能以这种方式成为泛型：

// This would be great
private void DoCopyToChildrenCommand<T, U>(T ca) where T : CategoryAttributeVM<U>
{
    foreach (var item in CategoryAttributeVM2s.OfType<T>())
        item.Value = ca.Value;  // item.Value is type U, which is perfect
}

// But this can't be, obviously
public RelayCommand<CategoryAttributeVM<U>> CopyToChildrenCommand<U> { get; private set; }

//这太好了
私有无效DoCopyToChildrenCommand（T ca），其中T:CategoryAttributeVM
{
foreach（CategoryAttributeVM2s.OfType（）中的变量项）
item.Value=ca.Value；//item.Value是U类型，这是完美的
}
//但这显然不可能
public RelayCommand CopyToChildrenCommand{get；private set；}

---

有什么想法吗？

我不能100%肯定我理解你的问题，但是为什么不在

RelayCommand

中使用

object

，只有当对象可以转换为你的泛型类型时，才能使

CanExecute（）

方法返回true

ICommand MyCommand { get; set; }

MyCommand = new RelayCommand<object>(
    param => DoCopyToChildrenCommand<T, U>(param as T),
    param => param is T);

ICommand MyCommand{get；set；}
MyCommand=新中继命令(
param=>DoCopyToChildrenCommand（参数为T），
param=>param是T）；

最后，我在

CategoryAttributeVM

和

CategoryAttributeVM

上添加了一个抽象方法重载：

---

谢谢你的回复。不幸的是，我没有提供给DoCopyToChildrenCommand的T和U类型

public abstract class CategoryAttributeVM 
{ 
    <...>
    public abstract void UpdateValueFrom(CategoryAttributeVM sourceCategoryAttributeVM);
} 

public abstract class CategoryAttributeVM<T> : CategoryAttributeVM 
{
    <...>
    public override void UpdateValueFrom(CategoryAttributeVM sourceCategoryAttributeVM)
    {
        if (GetType() == sourceCategoryAttributeVM.GetType())
            Value = (T)sourceCategoryAttributeVM.Value;
    }
}

private void DoCopyToChildrenCommand(CategoryAttributeVM ca)
{
    foreach (var attribute in CategoryAttributeVM2s)
        attribute.UpdateValueFrom(ca);
}