c# class reference as opposed to instance referenc

问题:

Can I locally reference a class in C#, instead of an instance of a class? The following code won't compile but, as an example, something like:

void someFunc()
{
    var a = System.Math;
    var b = a.Abs(4);
}

edit: In the real program it's not the System.Math class and I'm wanting to construct the class and return the constructed value. I didn't think originally that the context in which I wanted to use the class would be relevent, and probably it shouldn't be.

Anastasiosyal has an interesting idea with using a local Delegate to do it.

回答1:

You cannot assign a variable a value of a static class. The question is why would you want to do this, there are probably other ways that you could tackle your problem

e.g. you could use delegates to assign the operation you want to perform:

Func<int,int> operation = Math.Abs; 
// then you could use it like so: 
int processedValue = operation(-1);

回答2:

You can reference a class:

Type math = typeof(System.Math);

But you cannot call static methods on it using regular dot syntax:

// Wont compile:
math.Abs(5);

If you just want to shorten (and IMHO obfuscate) your code, you can reference classes with aliases via a using directive:

// Untested, but should work
namespace MyUnreadableCode {
    using m = System.Math;
    class Foo {
        public static Int32 Absolut(Int32 a) {
            return m.Abs(a);
        }
    }
}

回答3:

In c# they're called Types. And you can assign them like:

Type a = typeof(SomeClass);

However, you would have to instantiate it to use it. What I believe you want is a static import like in java, but unfortunately, they do not exist in c#.

Short answer: Not like what you have above.

回答4:

In C# 6.0 they introduced a static import feature, which can solve the problem.

using static System.Math;

class MyProgram
{
    static void Main(string[] args)
    {
        var b = Abs(4); // No need to specify the name of Math class
    }
}

回答5:

As I understand you need to refer to the class with short name? try this (on top of the file, inside using statements section):

using m = System.Math;

later in your code:

m.Abs(...)

Makes sense?

回答6:

No. It's not possible to treat a Type as a value where instance methods bind to static methods on the original type. In order to do this you would need to construct a new type which forwards it's method calls to the original type.

class MyMath { 
  public int Abs(int i) {
    return Math.Abs(i);
  }
}

var x = new MyMath();