c#如何显式实现接口成员

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 = 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
*/

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

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