如何显式实现接口成员（C# 编程指南）

  • 项目

本示例声明一个接口IDimensions 和一个类 Box，显式实现了接口成员 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 = 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，注释掉了 Main 方法中以下行，因为它们将产生编译错误。 显式实现的接口成员不能从类实例访问：

    //System.Console.WriteLine("Length: {0}", box1.GetLength());
//System.Console.WriteLine("Width: {0}", box1.GetWidth());

  • 另请注意 Main 方法中的以下行成功输出了框的尺寸，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());

另请参阅