实体框架-具有相同数据的两个人

Question

I want to map a two tables in entity framework 6 and need some help! It is for my chat application; I need to map user conversations into the database. Both group and private messages. For this question however, if you help me with the private messaging mapping, I should hopefully work out the group by myself :) anyway....

Each user can talk to any other user. They however share the same data, which is where I am struggling a bit: how to set the keys to the exact same data without duplication. This is what I have so far: * * EDIT - new code ** * **

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity;

namespace CodeFirstNewDatabaseSample
{
    static void Main(string[] args)
        {
            using(var db = new PrivateMessageContext()) 
            {
                Console.Write("Enter message: ");
                var message = Console.ReadLine();
                var userFrom = "userFrom";
                var userTo = "userTo";
                var messageDetail = new PrivateMessageDetail(MessageDate = DateTime.Now, FromUser = userFrom, message = message);
                var pm = new PrivateMessageHeader { User1 = userFrom, User2 = userTo, TimeStamp = DateTime.Now }; 
                pm.Messages.Add(messageDetail);
                db.PrivateMessages.Add(pm);
                db.SaveChanges();

                // Display all Blogs from the database 
                foreach(var pmsg in db.PrivateMessages)
                {
                    var query = pmsg;
                    Console.WriteLine(pmsg.Message);
                }
                Console.ReadKey(); 
        }
    }
}
public class PrivateMessage
{
    public int PrivateMessageId { get; set; }
    public string Message { get; set; }
    public DateTime TimeStamp { get; set; }

   // public int User1Id { get; set; }
    public virtual string user1 { get; set; }
   // public virtual User user1 { get; set; }
   public virtual string user2 { get; set; }
    //public int User1Id { get; set; }
   // public virtual User user2 { get; set; }
}
public class User
{
    public int UserId { get; set; }
    public string UserName { get; set; }
}
public class PrivateMessageContext : DbContext
{
    public DbSet<PrivateMessage> PrivateMessages { get; set; }
}
public class Send
{
 /*   void Send(userTo, userFrom, message) 
    {
        using (var db = new PrivateMessageContext()) {
            var query = from pm in db.PrivateMessages;
            foreach(var msg in pm)
            {
                var user1 = msg.user1;
                var user2 = msg.user2;
                if ( (user1==userTo && user2==userFrom) || (user1==userFrom && user2==userTo))
                {
                      msg.Message += message;
                      return;
                }
                else {
            // pair doesn't exist

                     var PrivateMessage = new PrivateMessage { user1 = userFrom; user2 = userTo; TimeStamp = DateTime.Now; Message = message; }; 
                     db.PrivateMessages.Add(PrivateMessage); 
                     db.SaveChanges(); 
                }
            }      
       }*/
}  

}

I am now stuck on two things - how to make a callable class which checks if there is previous message history (the Send() ) and how to use the User username instead of strings...

Thank you

* update 3 *

        static void Main(string[] args)
        {
            using(var db = new PrivateMessageContext()) 
            {
                Console.Write("Enter message: ");
                var message = Console.ReadLine();
                var userFrom = "userFrom";
                var userTo = "userTo";
                var messageDetail = new PrivateMessageDetail(MessageDate = DateTime.Now, FromUser = userFrom, message = message);
                var pm = new PrivateMessageHeader { User1 = userFrom, User2 = userTo, TimeStamp = DateTime.Now, Message = messageDetail }; 
                db.PrivateMessages.Add(pm);
                db.SaveChanges();

                // Display all Blogs from the database 
                foreach(var pmsg in db.PrivateMessages)
                {
                    var query = pmsg;
                    Console.WriteLine(pmsg.Message);
                }
                Console.ReadKey(); 
        }
    }
}
public class PrivateMessageContext : DbContext 
{ 
    public DbSet<PrivateMessageHeader> PrivateMessages { get; set; } 
} 

Answer 1

What you probably want is some kind of master/detail. What you would do is create a PrivateMessageHeader type, and this would contain the participants in the private message. Then you would have a PrivateMessageDetail type that would contain the actual messages. There would be a 1 to many association between Header and details.

So something like this:

public class PrivateMessageHeader {
    public PrivateMessageHeader() { Messages = new List<PrivateMessageDetail>; }
    public int PrivateMessageHeaderId {get;set;}
    public DateTime ThreadTime {get;set;} // Date of the start of thread
    public string User1 {get;set;}
    public string User2 {get;set;}  // this could be made to a list to allow multiples

    public ICollection<PrivateMessageDetail> Messages {get;set;}
}

public class PrivateMessageDetail {
    public int PrivateMessageDetailId {get;set;}
    public DateTime MessageDate {get;set;}
    public string FromUser {get;set;} // Don't need ToUser, it's already in header
    public string Message {get;set;}

    public PrivateMessageHeader parent {get;set;}
}