HOW TO：明確實作兩個介面的成員 (C# 程式設計手冊)
明確介面實作 (Implementation) 也可讓程式設計人員實作成員名稱相同的兩個介面，並針對每個介面成員提供獨立的實作。 這個範例同時以公制和英制單位顯示方塊的尺寸。 Box 類別會實作 IEnglishDimensions 和 IMetricDimensions 這兩個介面，它們代表不同的度量系統。 這兩個介面有相同的成員名稱：Length 和 Width。
範例
// 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
*/
穩固程式設計
如果您想要將英制單位做為預設的度量單位，請正常實作方法 Length 和 Width，並明確實作 IMetricDimensions 介面的 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;
}
在本範例中，您可以從類別執行個體中存取英制單位和從介面執行個體中存取公制單位：
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());
}