c# - 公共(public)密封类 SqlConnection : DbConnection, ICloneable

Question

请帮助我理解以下内容:

public sealed class SqlConnection : DbConnection, ICloneable {...}

在上面的课上我有两个疑惑

1. 在 C# 中，多重继承是不可能的(我们可以通过接口(interface)实现)。但是这里的 DBconnection 不是一个接口(interface)那么它是如何支持多重继承的呢？

2. Iclonable 是一个接口(interface)。它有一个名为 object Clone() 的方法。但是在 Sqlconnection 类中没有实现该方法。怎么可能？

请帮助我理解这一点

Answer 1

1. 这里没有多重继承。您可以继承一个类并实现多个接口(interface)。这里，DBConnection 是一个类，IClonable 是一个interface

2. IClonable 声明为 Explicit Interface ，这意味着您不能直接从类实例访问它，而必须显式转换为接口(interface)类型

示例

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());
    }
 }