如何应对GetDataPresent让它接受所有派生类型 [英] How to deal with GetDataPresent to let it accept all the derived types
问题描述
我使用 drgevent.Data.GetDataPresent 来确定被拖动组件是否是可以接受的还是不行。
I'm using drgevent.Data.GetDataPresent to determine whether the dragged component is acceptable or not.
我有一个问题,就是我要接受特定类型说SOMETYPE和所有从它派生的类型。似乎 GetDataPresent
不支持这样的要求。
I've got a problem which is that I want to accept a specific type say SomeType and all the types that derived from it. Seems GetDataPresent
doesn't support such requirement.
任何想法?
推荐答案
只要不使用GetDataPresent(),它是样板,但你可以自由地做你的方式。其实检索对象和检查,如果你很高兴与它的类型:
Just don't use GetDataPresent(), it is boilerplate but you're free to do it your way. Actually retrieve the object and check if you're happy with its type:
protected override void OnDragEnter(DragEventArgs drgevent) {
var obj = drgevent.Data.GetData(drgevent.Data.GetFormats()[0]);
if (typeof(Base).IsAssignableFrom(obj.GetType())) {
drgevent.Effect = DragDropEffects.Copy;
}
}
其中base是基类的名称。虽然使用GetFormats的()看起来很奇怪,这种做法是保证工作,因为拖着一个.NET对象只会产生的有一个的格式,因此对象类型的显示名称。这也是GetDataPresent不能派生对象的工作的原因。
Where Base is the name of the base class. While the use of GetFormats() looks odd, this approach is guaranteed to work because dragging a .NET object only ever produces one format, the display name of the type of the object. Which is also the reason that GetDataPresent can't work for derived objects.
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