C# Inheritance: How to invoke the base class constructor when i call the derived class constructor

Question

I am trying to figure out how to invoke a base class constructor when I call the derived class constructor.

I have a class called "AdditionalAttachment" which is inherited from System.Net.Mail.Attachment.I have added 2 more properties to my new class so that i can have all the properties of existing Attachment class with my new properties

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

Earlier i used to create constructor like

//objMs is a MemoryStream object

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

I am wondering how can I create the same kind of constructor to my class which will do the same thing as of the above constructor of the base class

Answer 1

This will pass your parameters into the base class's constructor:

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

You can write a constructor that calls the class base constructor:

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

Answer 3

Use this function:

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

Answer 4

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