如何：显式实现两个接口的成员（C# 编程指南）
显式接口实现还允许程序员实现具有相同成员名称的两个接口，并为每个接口成员各提供一个实现。 本示例同时以公制单位和英制单位显示框的尺寸。 Box 类实现 IEnglishDimensions 和 IMetricDimensions 两个接口，它们表示不同的度量系统。 两个接口有相同的成员名称 Length 和 Width。
示例
// Declare the English units interface:
interface IEnglishDimensions
{
float Length();
float Width();
}
// Declare the metric units interface:
interface IMetricDimensions
{
float Length();
float Width();
}
// Declare the Box class that implements the two interfaces:
// IEnglishDimensions and IMetricDimensions:
class Box : IEnglishDimensions, IMetricDimensions
{
float lengthInches;
float widthInches;
public Box(float length, float width)
{
lengthInches = length;
widthInches = width;
}
// Explicitly implement the members of IEnglishDimensions:
float IEnglishDimensions.Length()
{
return lengthInches;
}
float IEnglishDimensions.Width()
{
return widthInches;
}
// Explicitly implement the members of IMetricDimensions:
float IMetricDimensions.Length()
{
return lengthInches * 2.54f;
}
float IMetricDimensions.Width()
{
return widthInches * 2.54f;
}
static void Main()
{
// Declare a class instance box1:
Box box1 = new Box(30.0f, 20.0f);
// Declare an instance of the English units interface:
IEnglishDimensions eDimensions = (IEnglishDimensions)box1;
// Declare an instance of the metric units interface:
IMetricDimensions mDimensions = (IMetricDimensions)box1;
// Print dimensions in English units:
System.Console.WriteLine("Length(in): {0}", eDimensions.Length());
System.Console.WriteLine("Width (in): {0}", eDimensions.Width());
// Print dimensions in metric units:
System.Console.WriteLine("Length(cm): {0}", mDimensions.Length());
System.Console.WriteLine("Width (cm): {0}", mDimensions.Width());
}
}
/* Output:
Length(in): 30
Width (in): 20
Length(cm): 76.2
Width (cm): 50.8
*/
可靠编程
如果希望默认度量采用英制单位，请正常实现 Length 和 Width 这两个方法，并从 IMetricDimensions 接口显式实现 Length 和 Width 方法：
// Normal implementation:
public float Length()
{
return lengthInches;
}
public float Width()
{
return widthInches;
}
// Explicit implementation:
float IMetricDimensions.Length()
{
return lengthInches * 2.54f;
}
float IMetricDimensions.Width()
{
return widthInches * 2.54f;
}
这种情况下，可以从类实例访问英制单位，而从接口实例访问公制单位：
public static void Test()
{
Box box1 = new Box(30.0f, 20.0f);
IMetricDimensions mDimensions = (IMetricDimensions)box1;
System.Console.WriteLine("Length(in): {0}", box1.Length());
System.Console.WriteLine("Width (in): {0}", box1.Width());
System.Console.WriteLine("Length(cm): {0}", mDimensions.Length());
System.Console.WriteLine("Width (cm): {0}", mDimensions.Width());
}