C#的Compiler Error CS1660

原文地址：http://stackoverflow.com/questions/3926500/base-invoke-with-delegates

问题：

I am invoking a delegate and I'm not very informed about how it works and I have compilation errors because of it (Compiler Error CS1660). This is the code I have for it:

base.Invoke( delegate { bool flag = (((this.layerPickPlaceProcess != null) && (this.robotComponent != null)) && ((((StateEnum) this.layerPickPlaceProcess.State) == StateEnum.Idle) || (((StateEnum) this.layerPickPlaceProcess.State) == StateEnum.Ready))) && ((((StateEnum) this.robotComponent.State) == StateEnum.Idle) || (((StateEnum) this.robotComponent.State) == StateEnum.Ready)); this.cmdManualPlace.Enabled = flag; });

原因：

this is because Invoke accepts Delegate which is not (sic!) a delegate type as far as the C# compiler is concerned. A delegate type should define a call signature, while Delegate does not and is just a common ancestor. The expression delegate { ... } has type... try to guess... anonymous delegate(if it was a method it would be method group). They are not delegate types either! But they can be implicitly converted to a delegate type that has a matching signature. And delegate types can be implicitly converted to Delegate.

Action is: public delegate void Action();

simply, chains:

• Anonymous method → Delegate: no conversion exists
• Anonymous method → Action: implicit conversion if signature matches
• Action → Delegate: implicit conversion (Action is descendant of Delegate)

Combine them:

• Anonymous method → Action → Delegate: it works!

尝试以下代码即可解决：

// MethodInvoker is also acceptable. Action action = delegate { bool flag = (((this.layerPickPlaceProcess != null) && (this.robotComponent != null)) && ((((StateEnum) this.layerPickPlaceProcess.State) == StateEnum.Idle) || (((StateEnum) this.layerPickPlaceProcess.State) == StateEnum.Ready))) && ((((StateEnum) this.robotComponent.State) == StateEnum.Idle) || (((StateEnum) this.robotComponent.State) == StateEnum.Ready)); this.cmdManualPlace.Enabled = flag; }; base.Invoke(action);