C # harm of reference type & quot;

The front-end time has just completed a project and finally has time to summarize and review it.

Project requirements: send emails to users. emails are classified into system emails and personal emails, which need to be sorted by time and unread in descending order.

At first, I thought this was a simple requirement. I created an object for the email:

Class Mail {

Private string _ title = string. Empty;

Public string Title {

Get {return _ title ;}

}

Private string _ message = string. Empty;

Public string Message {

Get {return _ message ;}
}

Private bool _ isRead = false;

Public bool IsRead {

Get {return _ isRead}

}

Privaite DateTime _ insertTime = DateTime. Now;

Public DateTime InsertTime {

Get {return _ insertTime ;}

}

}

Then List <Mail> listMails = new List <Mail> for Bubble Sorting (which has been sorted by time in descending order, and now only needs to be sorted by unread)

For (int I = 0, count1 = listMails. Count; I <count1; I ++ ){

For (int j = I + 1; j <count1; j ++ ){

If (listMails [I]. IsRead &&! ListMails [j]. IsRead ){

Mail temp = listMails [I];

ListMails [I] = listMails [j];

ListMails [j] = temp;

}

}

}

The results can be imagined and are not arranged in descending order of unread.

Method 1: perform in-depth copy of Mail:

[Serializable]

Class Mail: ICloneable {

Private string _ title = string. Empty;

Public string Title {

Get {return _ title ;}

}

Private string _ message = string. Empty;

Public string Message {

Get {return _ message ;}
}

Private bool _ isRead = false;

Public bool IsRead {

Get {return _ isRead}

}

Privaite DateTime _ insertTime = DateTime. Now;

Public DateTime InsertTime {

Get {return _ insertTime ;}

}

Public object Clone ()
{
Using (Stream objectStream = new MemoryStream ())
{
IFormatter formatter = new BinaryFormatter ();
Formatter. Serialize (objectStream, this );
ObjectStream. Seek (0, SeekOrigin. Begin );
Return formatter. Deserialize (objectStream) as Employee;
}
}

}

Then List <Mail> listMails = new List <Mail> for Bubble Sorting (which has been sorted by time in descending order, and now only needs to be sorted by unread)

For (int I = 0, count1 = listMails. Count; I <count1; I ++ ){

For (int j = I + 1; j <count1; j ++ ){

If (listMails [I]. IsRead &&! ListMails [j]. IsRead ){

Mail temp = (Mail) listMails [I]. Clone ();

ListMails [I] = (Mail) listMails [j]. Clone ();

ListMails [j] = temp;

}

}

}

The result still does not work. It is depressing.

 

Finally, the value type (struct) is used for processing:

Struct Mail {

Private string _ title;

Public string Title {

Get {return _ title ;}

}

Private string _ message;

Public string Message {

Get {return _ message ;}
}

Private bool _ isRead;

Public bool IsRead {

Get {return _ isRead}

}

Privaite DateTime _ insertTime;

Public DateTime InsertTime {

Get {return _ insertTime ;}

}

}

Then List <Mail> listMails = new List <Mail> for Bubble Sorting (which has been sorted by time in descending order, and now only needs to be sorted by unread)

For (int I = 0, count1 = listMails. Count; I <count1; I ++ ){

For (int j = I + 1; j <count1; j ++ ){

If (listMails [I]. IsRead &&! ListMails [j]. IsRead ){

Mail temp = listMails [I];

ListMails [I] = listMails [j];

ListMails [j] = temp;

}

}

}

Test, all OK, we recommend that all students have a deep understanding of the value type and reference type to avoid unnecessary trouble.

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