How to: Explicitly Implement Interface Members with Inheritance (C# Programming Guide)

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。

// 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());
}