如何转换Func <T,bool> 表达 <Func<T,bool> &gt;

Question

I have a Func like this :

 Func<MyClass, bool> func = x=>Id == 5;

How I can convert it to :

 Expression<Func<MyClass, bool>>

Answer 1

You can just write:

Expression<Func<MyClass,bool>> expr = x=>Id == 5;

This will set expr to be an expression tree for Id == 5 .

If you do:

Func<MyClass, bool> func = x=>Id == 5;
Expression<Func<MyClass, bool>> expr = mc => func(mc);

Then this will set expr to be an expression tree for a call to func , not an expression tree for the body of func .

Answer 2

Try this:

Func<MyClass, bool> func = x=>Id == 5;
Expression<Func<MyClass, bool>> expr = mc => func(mc);

Answer 3

You can create an expression that represents the call to the delegate you created. But most of the time, when you're using Expression s, you do that to understand what the code does (eg to convert it to SQL). And you can't do that with an expression to invoke an opaque function.