C＃繼承：當我調用派生類構造函數時如何調用基類構造函數

Question

我想弄清楚當我調用派生類構造函數時如何調用基類構造函數。

我有一個名爲「AdditionalAttachment」的類，它繼承自System.Net.Mail.Attachment.I爲我的新類增加了2個屬性，這樣我就可以使用我的新屬性獲得現有Attachment類的所有屬性

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

早些時候我曾經喜歡

// objMs創建構造函數是一個MemoryStream對象

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

我想知道我怎麼可以創造同一種構造上我的課，這將做同樣的事情作爲基類的上述構造的

Answer 1

這將通過你的參數爲基類的構造函數：

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

您可以編寫調用基類構造函數的構造函數：

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) 
{ 
}