Zyan+EF6+SqlCe4 concurrent data access example. Application source code (make sure you create a configuration file).

eftest3.cs

// Zyan + EF6 concurrent data access example.
// Written by Alexey Yakovlev <yallie@yandex.ru>
// Compile this code using: 
//
// csc eftest3.cs /r:Zyan.Communication.dll /r:EntityFramework.dll /r:EntityFramework.SqlServerCompact.dll /r:System.ComponentModel.DataAnnotations.dll
//
// First run — starts server.
// Second run — starts client.

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Data.Entity;
using System.Linq;
using System.Net.Sockets;
using System.Threading;
using System.Transactions;
using Zyan.Communication;
using Zyan.Communication.Protocols.Tcp;

class Program
{
	static void Main(string[] args)
	{
		try
		{
			RunServer();
		}
		catch (SocketException) // server already running
		{
			RunClient();
		}
	}

	// shared code ---------------

	interface IUserService
	{
		void AddUser(string name);
		IEnumerable<string> GetUsers();
	}

	// server code ---------------

	class User
	{
		[Key]
		public int ID { get; set; }
		public string Name { get; set; }
	}

	class UserContext : DbContext
	{
		public DbSet<User> Users { get; set; }
	}

	class UserService : IUserService
	{
		public void AddUser(string name)
		{
			Console.WriteLine("Adding user: {0}", name);
			var user = new User { Name = name };
			userContext.Users.Add(user);
			userContext.SaveChanges(); 

			if (name == "Dave")
			{
				// even if SaveChanges is already called, the transaction will be rolled back due to exception
				throw new InvalidOperationException("I'm sorry Dave, I'm afraid I can't do that.");
			}
		}

		public IEnumerable<string> GetUsers()
		{
			var query =
				from u in userContext.Users
				orderby u.Name
				select u.Name;

			return query.ToArray();
		}
	}

	static void RunServer()
	{
		using (var zyanHost = new ZyanComponentHost("EntityFrameworkServer", 8195))
		{
			zyanHost.RegisterComponent<IUserService, UserService>();
			zyanHost.BeforeInvoke += ZyanHost_BeforeInvoke;
			zyanHost.AfterInvoke += ZyanHost_AfterInvoke;
			zyanHost.InvokeCanceled += ZyanHost_InvokeCanceled;

			Console.WriteLine("Trying to access the database...");
			using (var ctx = new UserContext())
			{
				var dummy = ctx.Users.Count();
			}

			Console.WriteLine("Server is ready. Press ENTER to stop.");
			Console.WriteLine();
			Console.WriteLine("Run the program again to test the concurrent database access.");
			Console.ReadLine();
		}
	}

	[ThreadStatic]
	static UserContext userContext;

	[ThreadStatic]
	static TransactionScope transactionScope;

	static void ZyanHost_BeforeInvoke(object sender, BeforeInvokeEventArgs args)
	{
		var options = new TransactionOptions
		{
			IsolationLevel = IsolationLevel.ReadCommitted,
			Timeout = TimeSpan.Zero
		};

		// begin a new transaction and create a data context
		transactionScope = new TransactionScope(TransactionScopeOption.RequiresNew, options);
		userContext = new UserContext();
	}

	static void ZyanHost_AfterInvoke(object sender, AfterInvokeEventArgs args)
	{
		// remote call was successful, commit the transaction
		if (transactionScope != null)
		{
			transactionScope.Complete();
			transactionScope.Dispose();
			transactionScope = null;
		}

		if (userContext != null)
		{
			userContext.Dispose();
			userContext = null;
		}
	}

	static void ZyanHost_InvokeCanceled(object sender, InvokeCanceledEventArgs args)
	{
		// remote call failed, rollback the transaction
		if (transactionScope != null)
		{
			transactionScope.Dispose();
			transactionScope = null;
		}

		if (userContext != null)
		{
			userContext.Dispose();
			userContext = null;
		}
	}

	// client code ---------------

	static void RunClient()
	{
		var serverUrl = "tcp://localhost:8195/EntityFrameworkServer";
		Console.WriteLine("Connecting to {0}...", serverUrl);
		Console.WriteLine();

		using (var zyanConnection = new ZyanConnection(serverUrl))
		{
			var proxy = zyanConnection.CreateProxy<IUserService>();

			// inserting data concurrently
			Console.WriteLine("Spawning several threads to create multiple users...");
			var userNames = new[] { "Bob", "Alice", "Dave", "Erwin", "Charles", "Roger", "Steve" };
			for (var i = 0; i < 20; i++)
			{
				var index = i;
				ThreadPool.QueueUserWorkItem(x =>
				{
					var name = userNames[index % userNames.Length];
					Console.WriteLine("Adding {0}...", name);
					try
					{
						proxy.AddUser(name);
					}
					catch (Exception ex)
					{
						Console.WriteLine("Error inserting {0}. {1}", name, ex.InnerException.Message);
					}
				});
			}

			Console.WriteLine("Wait a minute, then press ENTER to continue.");
			Console.ReadLine();

			// selecting data
			var users = proxy.GetUsers();
			Console.WriteLine("{0} users in the database: {1}", users.Count(), string.Join(", ", users));
			Console.WriteLine();
			Console.WriteLine("Notice there are no Daves.");
			Console.ReadLine();
		}
	}
}