Question

我在VS2010中有两个用于实现接口的选项。

enter image description here

当我有IHelper.cs界面时如下：

public interface IHelper
    ....
    IEnumerable<IPort> Ports { get; }

“明确实现接口”给出了以下代码：

    IEnumerable<IPort> IHelper.Ports
    {
        get
        {
            ...
        }
    }

而且，“实现接口”给了我这段代码：

    public IEnumerable<IPort> Ports
    {
        get
        {
            ...
        }
    }

它们是相同还是不同？为什么我在C＃中实现接口有两种选择？

Answer 1

显式接口声明意味着接口成员在接口本身以外的类型上不可用，因此在公开访问它们之前，需要将实现类型强制转换为接口。

Implicit是实现大多数接口的标准方式，它在implementsor-type的公共API上公开接口项。

显式接口定义的主要原因是为了避免命名冲突，如果您碰巧实现了包含具有相同签名的方法的两个接口...显式定义允许编译器保持签名不同足以解决。

支持代码维护的第二个原因，如注释中XenoPuTtSs所建议的那样，如果删除方法签名，显式定义将触发实现类型上的编译器错误。在隐式实现中，从接口中删除方法将使方法成为任何类型的常规成员 - 这意味着您需要手动搜索现在已解散的方法实现。

Answer 2

他们完全不同。如果明确地实现接口，则只能通过引用该接口来引用接口成员。以下代码演示了这个想法。

public interface IFoo {
    String Bar { get; set; }
}
public class ImplicitFoo : IFoo {
    public string Bar {get;set;}
}
public class ExplicitFoo : IFoo {
    private String _Bar;
    string IFoo.Bar {
        get {
            return _Bar;
        }
        set {
            _Bar = value;
        }
    }
}
public class Test {
    public void Test() {
        var iml = new ImplicitFoo();
        // Works fine
        Console.WriteLine(iml.Bar);
        var expl = new ExplicitFoo();
        var fooInterface = (IFoo)expl;
        // Works fine
        Console.WriteLine(fooInterface.Bar);
        // Throws compile time exception
        Console.WriteLine(expl.Bar);
    }
}

Answer 3

实现接口的类可以显式实现该接口的成员。显式实现成员时，不能通过类实例访问它，而只能通过接口的实例访问它。

// explicit1.cs
interface IDimensions 
{
  float Length();
  float Width();
}

class Box : IDimensions 
{
  float lengthInches;
  float widthInches;

 public Box(float length, float width) 
 {
    lengthInches = length;
   widthInches = width;
 }
 // Explicit interface member implementation: 
 float IDimensions.Length() 
 {
    return lengthInches;
 }
 // Explicit interface member implementation:
 float IDimensions.Width() 
 {
    return widthInches;      
 }

 public static void Main() 
 {
   // Declare a class instance "myBox":
   Box myBox = new Box(30.0f, 20.0f);
  // Declare an interface instance "myDimensions":
  IDimensions myDimensions = (IDimensions) myBox;
  // Print out the dimensions of the box:
  /* 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}", myBox.Length());
  //System.Console.WriteLine("Width: {0}", myBox.Width());
  /* Print out the dimensions of the box by calling the methods 
     from an instance of the interface:                         */
  System.Console.WriteLine("Length: {0}", myDimensions.Length());
  System.Console.WriteLine("Width: {0}", myDimensions.Width());
 }
}

显式接口实现还允许程序员继承两个共享相同成员名称的接口，并为每个接口成员提供单独的实现。此示例以公制和英制单位显示框的尺寸。 Box类继承了两个接口IEnglishDimensions和IMetricDimensions，它们代表不同的测量系统。两个接口都具有相同的成员名称，长度和宽度。

查看示例

// explicit2.cs
// 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;
}
public static void Main() 
{
  // Declare a class instance "myBox":
  Box myBox = new Box(30.0f, 20.0f);
  // Declare an instance of the English units interface:
  IEnglishDimensions eDimensions = (IEnglishDimensions) myBox;
  // Declare an instance of the metric units interface:
  IMetricDimensions mDimensions = (IMetricDimensions) myBox;
  // 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());
 }
}

有关详细信息，请查看此article

在C＃中明确实现接口与实现接口

3 个答案: