大神解惑。。。。

//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。
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
//-----------------------------------------output-----------------------------------------//