C＃| Type.IsAssignableFrom(Type)方法

Type.IsAssignableFrom(Type)方法用于确定是否可以将指定类型的实例分配给当前类型的变量。

Syntax: public virtual bool IsAssignableFrom (Type c);
Here, it takes the type to compare with the current type.

Return Value: This method returns true if any of the following conditions is true:

• c and the current instance represent the same type.
• c is derived either directly or indirectly from the current instance. c is derived directly from the current instance if it inherits from the current instance; c is derived indirectly from the current instance if it inherits from a succession of one or more classes that inherit from the current instance.
• The current instance is an interface that c implements.
• c is a generic type parameter, and the current instance represents one of the constraints of c.

下面的程序说明了Type.IsAssignableFrom()方法的用法：

范例1：

// C# program to demonstrate the
// Type.IsAssignableFrom() Method
using System;
using System.Globalization;
using System.Reflection;
using System.IO;
  
// Defining MyClass extended
// from TypeDelegator
public class MyClass : TypeDelegator { }
  
class GFG {
  
    // Main Method
    public static void Main()
    {
        // Declaring and initializing object of Type
        Type objType = typeof(TypeDelegator);
  
        // Getting array of Properties by
        // using GetProperties() Method
        bool status = objType.IsAssignableFrom(typeof(MyClass));
  
        // Display the Result
        if (status)
            Console.WriteLine("Instance of a specified type can be "
                   + "assigned to a variable of the current type.");
        else
            Console.WriteLine("Instance of a specified type can't be "
                     + "assigned to a variable of the current type.");
    }
}

输出：

Instance of a specified type can be assigned to a variable of the current type.

范例2：

// C# program to demonstrate the
// Type.IsAssignableFrom() Method
using System;
using System.Globalization;
using System.Reflection;
using System.IO;
  
class GFG {
  
    // Main Method
    public static void Main()
    {
        // Declaring and initializing object of Type
        Type objType = typeof(double);
  
        // Getting array of Properties by
        // using GetProperties() Method
        bool status = objType.IsAssignableFrom(typeof(int));
  
        // Display the Result
        if (status)
            Console.WriteLine("Instance of a specified type can be "
                   + "assigned to a variable of the current type.");
        else
            Console.WriteLine("Instance of a specified type can't be "
                     + "assigned to a variable of the current type.");
    }
}

输出：

Instance of a specified type can't be assigned to a variable of the current type.

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.type.isassignablefrom?view=netframework-4.8