使用 c# 泛型扩展方法对类而不是集合进行操作

Question

I have the following types defined:
-----------------------------------

interface IMyInterface<T> where T : class
{
   void BlahBlah();
}
abstract class MyBase<T> : IMyInterface<T> where T : class
{
   public abstract T MyInfo { get; set; }
   public abstract T MyInfo2 { get; set; }
   public void BlahBlah()
   {
       Console.WriteLine(MyInfo + ", " + MyInfo2);
   }
}
class MyConcreteClass1<T> : MyBase<T> where T : class
{
   public override T MyInfo { get; set; }
   public override T MyInfo2 { get; set; }
}
class MyConcreteClass2<T> : MyBase<T> where T : class
{
   public override T MyInfo { get; set; }
   public override T MyInfo2 { get; set; }
}


public static class DataOperations<T, U> where T : class where U : class
{
        public static U Operate(this T source, U destination)
        {
            var sourceProps = source.GetType().GetProperties();
            var destinationProps = destination.GetType().GetProperties();

                .
                .
                .
            return destination;
        }
}

What I'm trying to do is to do in the implementation is to operate on two of the above classes as so:

MyConcreteClass1<String> class1 = new MyConcreteClass1<String>();
class1.MyInfo = "Some Value";
class1.MyInfo2 = "another value";
MyConcreteClass2<String> class2 = new MyConcreteClass2<String>();
var c2 = class1.Operate(class2);

The problem is that I get: "CS1106 Extension method must be defined in a non-generic static class" on DataOperations class name.

Answer 1

The declaring type must be be non-generic, but the method can be generic. Consider instead:

public static class DataOperations
{
        public static U Operate<T, U>(this T source, U destination)
             where T : class where U : class
        { // ...
        }
}

Answer 2

Move the generic definitions onto the method:

public static class DataOperations
{
        public static U Operate<T, U>(this T source, U destination)  where T : class where U : class
        {
            // Whatever
        }
}

Answer 3

Extension methods have to be defined - as the error states - in a non-generic static (top-level) class.

So you need to make the DataOperations class non-generic and the method itself generic instead:

public static class DataOperations
{
        public static U Operate<T, U>(this T source, U destination) where T : class where U : class

        {
            var sourceProps = source.GetType().GetProperties();
            var destinationProps = destination.GetType().GetProperties();

                .
                .
                .
            return destination;
        }
}