如何使用相同類型的參數關閉類型是否可分配給開放泛型類型？

Question

我需要一個方法，如果傳入的類型可分配給（派生自）開放（無界）泛型類型的閉包，則返回true。該方法應該如下工作：

OpenGenericIsAssignableFrom(typeof(ICollection<>), typeof(IList<String>)) 

應該返回true。

Answer 1

擴展Check if a class is derived from a generic class，這裏是一個可能的解決方案：

 private static bool OpenGenericIsAssignableFrom1(Type openGenericType, Type typeToCheck) 
     { 
      return typeToCheck != null && typeToCheck != typeof(Object) && // Terminate recursion 
       ((typeToCheck.IsGenericType && (typeToCheck.GetGenericTypeDefinition() == openGenericType)) || // typeToCheck is as closure of openGenericType 
       OpenGenericIsAssignableFrom(openGenericType, typeToCheck.BaseType) || // typeToCheck is the subclass of a closure of openGenericType 
       typeToCheck.GetInterfaces().Any(interfaceType => OpenGenericIsAssignableFrom(openGenericType, interfaceType))); // typeToCheck inherits from an interface which is the closure of openGenericType 
     } 

Answer 2

爲什麼不乾脆關閉打開的泛型類型，看看是否是從封閉式assingable？美中不足的是，在相同的參數關閉它可能是無效的，所以你就需要趕上

private static bool OpenGenericIsAssignableFrom(
    Type openGenericType, 
    Type typeToCheck) 
{ 
    if (!openGenericType.IsGenericType || typeToCheck == null) return false; 

    if(typeToCheck.IsGenericType) 
    { 
     var typeArgs = typeToCheck.GetGenericArguments(); 
     if (typeArgs.Length == openGenericType.GetGenericArguments().Length) 
     { 
      try 
      { 
       var closed = openGenericType.MakeGenericType(typeArgs); 
       return closed.IsAssignableFrom(typeToCheck); 
      } 
      catch 
      { 
       //violated type contraints 
       return false 
      } 
     } 
    } 
    else 
    { 
     return OpenGenericIsAssignableFrom(openGenericType, typeToCheck.BaseType) 
       || typeToCheck.GetInterfaces() 
        .Any(i=> OpenGenericIsAssignableFrom(openGenericType,i)); 
    } 
}