如何:显式实现接口成员(C# 编程指南)

本示例声明一个 接口 IDimensions 和一个类 Box,该类显式实现接口成员 getLength 和 getWidth。 通过接口实例 dimensions 访问这些成员。

示例

interface IDimensions
{
    float getLength();
    float getWidth();
}

class Box : IDimensions
{
    float lengthInches;
    float widthInches;

    Box(float length, float width)
    {
        lengthInches = length;
        widthInches = width;
    }
    // Explicit interface member implementation: 
    float IDimensions.getLength()
    {
        return lengthInches;
    }
    // Explicit interface member implementation:
    float IDimensions.getWidth()
    {
        return widthInches;
    }

    static void Main()
    {
        // Declare a class instance box1:
        Box box1 = new Box(30.0f, 20.0f);

        // Declare an interface instance dimensions:
        IDimensions dimensions = (IDimensions)box1;

        // The following commented lines would produce compilation 
        // errors because they try to access an explicitly implemented
        // interface member from a class instance:                   
        //System.Console.WriteLine("Length: {0}", box1.getLength());
        //System.Console.WriteLine("Width: {0}", box1.getWidth());

        // Print out the dimensions of the box by calling the methods 
        // from an instance of the interface:
        System.Console.WriteLine("Length: {0}", dimensions.getLength());
        System.Console.WriteLine("Width: {0}", dimensions.getWidth());
    }
}
/* Output:
    Length: 30
    Width: 20
*/

可靠编程

  • 请注意 Main 方法中下列代码行被注释掉,因为它们将产生编译错误。 显式实现的接口成员不能从实例访问:

    //System.Console.WriteLine("Length: {0}", box1.getLength());
    //System.Console.WriteLine("Width: {0}", box1.getWidth());
    
  • 还请注意,Main 方法中的下列代码行成功输出框的尺寸,因为这些方法是从接口实例调用的:

    System.Console.WriteLine("Length: {0}", dimensions.getLength());
    System.Console.WriteLine("Width: {0}", dimensions.getWidth());
    

请参见

任务

如何:显式实现两个接口的成员(C# 编程指南)

参考

类和结构(C# 编程指南)

接口(C# 编程指南)

概念

C# 编程指南