我正在使用应用于 ItemsControl 项目的隐式数据模板:
<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>
这是数据绑定(bind)到我的 ViewModel 的,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
}
}
}
如何从 CategoryAttributeVM2 中获取与“ca”类型匹配的对象?
我想我错过了一些基本的东西,但看不到它。
泛型方法会很好,但AFAIK RelayCommand 不能以这种方式通用:
// 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; }
有任何想法吗?
最佳答案
我不是 100% 确定我理解你的问题,但为什么不使用 object
在您的 RelayCommand
并制作 CanExecute()
仅当对象可以转换为您的泛型类型时,方法才返回 true?
ICommand MyCommand { get; set; }
MyCommand = new RelayCommand<object>(
param => DoCopyToChildrenCommand<T, U>(param as T),
param => param is T);
关于c# - 通过 MVVM Light RelayCommand 绑定(bind)泛型类型,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8988875/