[英]Generic Method returning different generic collections
Hi I have a Method like this: 嗨我有这样的方法:
public T LoadR<T, K>()
where T : ObservableCollection<K>, new()
where K : IStoreElement, new() {
T onC = new T();
//....
return (onC);
}
Further I have a class XObservableCollection which derivies from ObservableCollection. 此外,我有一个XObservableCollection类,它派生自ObservableCollection。 It works as it is when I call:
当我打电话时,它的工作原理是:
Categories = LoadR<ObservableCollection<Category>,Category>();
Products = LoadR<XObservableCollection<Product>,Product>();
What I want to do is to make a call like this (avoid passing the K as extra parameter): 我想要做的就是这样做一个调用(避免将K作为额外参数传递):
Categories = LoadR<ObservableCollection<Category>>();
Products = LoadR<XObservableCollection<Product>>();
I know that I could write an extension for it. 我知道我可以为它写一个扩展名。 But I curious if there is a way to achive this without it.
但我很好奇是否有办法在没有它的情况下实现这一目标。
Manfred 曼弗雷德
I don't think you can. 我认为你不能。
C# has a mechanism to understand generic agruments from method paramaters when used in it, but not from other generic arguments of the same method. C#有一种机制来理解方法参数中使用的泛型agruments,而不是来自同一方法的其他泛型参数。 It doesn't work.
它不起作用。
Maybe you can change your signature to: 也许您可以将签名更改为:
private static ObservableCollection<K> LoadR<K>(.ObservableCollection<K> onC)
where K : IStoreElement, new()
{
//....
return onC;
}
Usage would be: 用法是:
static void TestLoad()
{
var result1 = LoadR(new ObservableCollection<Something>());
var result2 = LoadR(new DerivedClassFromObservableCollection<Something>());
}
Which I agree is not that good, and I can se it's not what you are looking for. 我同意的不是那么好,我可以认为它不是你想要的。
But just because C# wouldn't let you try to infer the types from the generic arguments. 但只是因为C# 不会让你尝试从泛型参数中推断出类型。
..... .....
The other way aroudn is to make it use a specific collection. 另一种方式是使它使用特定的集合。 I can see you don't want this even more.
我可以看到你不想要这个。
So, one thing you can do is make it return IEnumerable instead, then you usage will be something like: 所以,你可以做的一件事是让它返回IEnumerable,然后你的用法将是这样的:
static void TestLoad()
{
var result1 = new ObservableCollection( LoadR<Something>() );
var result1 = new DerivedClassFromObservableCollection( LoadR<Something>() );
}
Which may not be good also if you want to do fancy things with the collection itself, because you no-longer own it. 如果你想用收藏本身做一些奇特的东西,那也许不好,因为你不再拥有它。
.... ....
I would go for the very first option myself. 我自己会选择第一个选项。
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