how to combine query results of several times function call with entity framework5? - linq

Question

i want to use a function to query db with linq and combine their results,i write the code as follows but cannot work , any one can help me? thanks!
the error:(The operation cannot be completed because the DbContext has been disposed)
the part code:
public static IEnumerable<UserLocation> loadedUserList;
public static IEnumerable<UserLocation> combinedUserList;
public static void loadDataInStaticClass()
{
using (var context = new SptialTestEntities())
{
var loadedUserList = from newRcords in context.UserLocations
where newRcords.ID > lastLoadedID
select newRcords;
if (loadedUserList.Any())
{
foreach (var user in loadedUserList)
{
Console.WriteLine(user.UserName);
}
if (combinedUserList != null)
{
combinedUserList = loadedUserList.Union(combinedUserList);
foreach (var cc in combinedUserList)
{
Console.WriteLine("\n after combined：" + cc.UserName);
}
}
else
{
combinedUserList = loadedUserList;
Console.WriteLine("\nfirst run ：" + combinedUserList.Count());
foreach (var cc in combinedUserList)
{
Console.WriteLine("\n user:" + cc.UserName);
}
}
}
}
}
the problem is: the first call is ok, but the second report error: The operation cannot be completed because the DbContext has been disposed ,and how?
thanks!

Answer 1

i paste the whole code and some one can run and check the mistake and thank u:
userLocation a table contain userid,username,userlocation(geography type) ,and
i user database first mode in visual studio 2012 and map the userLocation to a entity of SptialTestEntities.
Program.cs
static void Main(string[] args)
{
for (int i = 1; i < 3; i++)
{
Console.WriteLine("\nrun{0}times, i);
Test.LoadUsersFromDB();
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Data.Spatial;
using System.Data.Entity;
using System.Xml.Linq;
using System.IO;
using System.Configuration;
using System.Web;
using System.Web.Script.Serialization;
using System.Collections;
using System.Globalization;
namespace SptialMatch
{
class Test
{
public static int lastedLoadedRecordID = 14;
public static IEnumerable<UserLocation> loadedUserList;
public static IEnumerable<UserLocation> combinedUserList;
public static void LoadUsersFromDB()
{
try
{
Console.WriteLine("\n------------------------load data begin----------------------------------------------------------");
//var context = new SptialTestEntities();
using (var context = new SptialTestEntities())
{
System.Diagnostics.Stopwatch loadStopwatch = new System.Diagnostics.Stopwatch();
loadStopwatch.Start();
loadedUserList = from newRcords in context.UserLocations
where newRcords.ID > lastedLoadedRecordID
select newRcords;
if (loadedUserList.Any())
{
foreach (var loadUser in loadedUserList)
{
Console.WriteLine("\n loaded element：" + loadUser.UserName);
}
if (combinedUserList != null)
{
Console.WriteLine("\nnot first run：" );
foreach (var cc in combinedUserList)
{
Console.WriteLine("\n before union：" + cc.UserName);
}
IEnumerable<UserLocation> tmp = loadedUserList.AsEnumerable();
combinedUserList = tmp.Union<UserLocation>(combinedUserList.AsEnumerable(), new UserComparer2()).ToList();
Console.WriteLine("\nnot first run after union：" );
foreach (var cc in combinedUserList)
{
Console.WriteLine("\n after union the user name is：" + cc.UserName);
}
}
else
{
combinedUserList = loadedUserList;
Console.WriteLine("\nfirst run the count is：" + combinedUserList.Count());
foreach (var cc in combinedUserList)
{
Console.WriteLine("\n the combined list：" + cc.UserName);
}
}
var maxID = loadedUserList.Max(myMaxID => myMaxID.ID);
lastedLoadedRecordID = lastedLoadedRecordID + 1;
}
else
{
Console.WriteLine("\n no new data！");
Console.WriteLine("\n-----------------load end，no new data yet------------------------------------------------");
Thread.Sleep(3000);
}
loadStopwatch.Stop();
Console.WriteLine("\nload time cost{0} seconds。", loadStopwatch.Elapsed);
Console.WriteLine("\n---------------------load end ----------------------------------------------------------");
}
}
catch (Exception ex)
{
Console.WriteLine("\n exception message：" + ex.Message);
}
}
}
class UserComparer2 : IEqualityComparer<UserLocation>
{
public bool Equals(UserLocation x, UserLocation y)
{
//Check whether the compared objects reference the same data.
if (Object.ReferenceEquals(x, y)) return true;
//Check whether any of the compared objects is null.
if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
return false;
//Check whether the products' properties are equal.
return x.ID == y.ID && x.UserName == y.UserName;
}
// If Equals() returns true for a pair of objects
// then GetHashCode() must return the same value for these objects.
public int GetHashCode(UserLocation user)
{
//Check whether the object is null
if (Object.ReferenceEquals(user, null)) return 0;
//Get hash code for the Name field if it is not null.
int hashUserName = user.UserName == null ? 0 : user.UserName.GetHashCode();
//Get hash code for the Code field.
int hashUserCode = user.ID.GetHashCode();
//Calculate the hash code for the product.
return hashUserName ^ hashUserCode;
}
}
}