why are lambdas & anonymous methods not allowed on the left side of the is or as operator?

Question

Lambdas are not allowed on the left side of the is or as operator. MSDN

A clear explanation with an real example would be appreciated?

Answer 1

Lambda没有类型，因此，使用检查没有type的值的类型的运算符是没有意义的。

Answer 2

I suspect that it's not related to the following case:

Func<string> x = () => "";  
bool result = x is Func<string>;

But to this case:

// This won't compile
if((() => "") is Func<string>)
{
}

...or:

// This won't compile too
Func<string> func = (() => "") as Func<string>;

Lambda expressions and anonymous methods have no type per se, but they're useful when using delegate type auto-inference:

// C# compiler understands that the right part should be Func<string>
// because the expression signature and return value matches Func<string>
Func<string> func = () => "hello world";

MSDN states that is and as can't be used with anonymous methods and lambda expressions because they've no type until they're infered to some actual delegate type or expression tree.