C＃继承：当我调用派生类构造函数时如何调用基类构造函数

Question

我想弄清楚当我调用派生类构造函数时如何调用基类构造函数。

我有一个名为“AdditionalAttachment”的类，它继承自System.Net.Mail.Attachment.I为我的新类增加了2个属性，这样我就可以使用我的新属性获得现有Attachment类的所有属性

public class AdditionalAttachment: Attachment 
{ 
    [DataMember] 
    public string AttachmentURL 
    { 
     set; 
     get; 
    } 
    [DataMember] 
    public string DisplayName 
    { 
     set; 
     get; 
    } 
} 

早些时候我曾经喜欢

// objMs创建构造函数是一个MemoryStream对象

Attachment objAttachment = new Attachment(objMs, "somename.pdf") 

我想知道我怎么可以创造同一种构造上我的课，这将做同样的事情作为基类的上述构造的

Answer 1

这将通过你的参数为基类的构造函数：

public AdditionalAttachment(MemoryStream objMs, string displayName) : base(objMs, displayName) 
{ 
    // and you can do anything you want additionally 
    // here (the base class's constructor will have 
    // already done its work by the time you get here) 
} 

Answer 2

public class AdditionalAttachment: Attachment 
{ 
    public AdditionalAttachment(param1, param2) : base(param1, param2){} 
    [DataMember] 
    public string AttachmentURL 
    { 
     set; 
     get; 
    } 
    [DataMember] 
    public string DisplayName 
    { 
     set; 
     get; 
    } 
} 

Answer 3

您可以编写调用基类构造函数的构造函数：

public AdditionalAttachment(MemoryStream objMs, string filename) 
    : base(objMs, filename) 
{ 
} 

Answer 4

使用此功能：

public AdditionalAttachment(MemoryStream ms, string name, etc...) 
     : base(ms, name) 
{ 
}