WCF GET方法无法获取iOS客户端的最新数据

我的WCF服务和iOS客户端遇到了一个奇怪的情况，我真的不知道发生了什么。问题是，如果我在客户端中使用WCF POST方法添加数据，然后调用GET从该表中获取所有数据，则POST中的所有数据都不会返回给客户端。进一步说明:

1. 假设表Users有一个用户John
2. 我调用GET方法从表中获取所有用户。
3. John出现在我的iOS客户端。
4. 现在我从我的iOS客户端POST，添加用户Mike
5. Mike出现在数据库中，POST操作成功。
6. 我再次为所有用户调用GET方法，但这次Mike没有出现在

我还注意到，如果我从iPhone上删除应用程序，然后用Xcode将其添加回来，然后运行GET方法，从Users表返回所有数据。我不确定数据是否被缓存在某个地方或什么。我怀疑问题可能是在我的客户端代码如何运行GET，但我不完全确定，它可能是我的服务器代码。下面是我的代码。

//服务代码

//IService.cs

  [OperationContract]
        [WebInvoke(Method ="GET", ResponseFormat= WebMessageFormat.Json, BodyStyle= WebMessageBodyStyle.WrappedResponse, UriTemplate = "/GetUsers")]
        string GetMyUsers();
[OperationContract]
    [WebInvoke(Method = "POST", RequestFormat=WebMessageFormat.Json, BodyStyle=WebMessageBodyStyle.WrappedRequest, ResponseFormat = WebMessageFormat.Json, UriTemplate = "/NewUser")]
    string AddNewUser(NewUser newUser);

[DataContract]
public class NewUser
{
    [DataMember(Name="name")]
    public string name { get; set; }

    [DataMember(Name="age")]
    public string age { get; set; }
}

//Service1.svc.cs

 public  string AddNewUser(NewUser newUser)
        {
            var userController = new UserController();
            userController.AddNewUser(newUser.name, newUser.age);
            return "Method Call Complete";
        }
   public string GetMyUsers()
        {
            var userController = new UserController();
            string returnString = userController.GetAllUsers();
            return returnString;
        }

//UserController.cs

  public string GetAllUsers()
        {
            using(var db = new EmployeesEntities1())
            {
                string returnString = string.Empty;
                List<User> userList = db.Users.ToList();
                JavaScriptSerializer jss = new JavaScriptSerializer();
                returnString = jss.Serialize(userList);
                return returnString;
            }
        }

//IOS客户端GET

NSString *restCallString = [NSString stringWithFormat:@"http://myPublicIP/MyService/Service1.svc/GetUsers"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:restCallString]];
[request setHTTPMethod:@"GET"];
[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
NSError *error = nil;
NSURLResponse *response = nil;
NSData *result = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSDictionary *jsonArray=[NSJSONSerialization JSONObjectWithData:result options:0 error:nil];
NSString  *item = [jsonArray objectForKey:@"GetMyUsersResult"];
txtData.text = item;

//IOS客户端POST

  NSArray *propertyNames = [NSArray arrayWithObjects:@"name", @"age",nil];
    NSArray *propertyValues = [NSArray arrayWithObjects:@"Mike", @"23",nil];
    NSDictionary *properties = [NSDictionary dictionaryWithObjects: propertyValues forKeys:propertyNames];
    NSMutableDictionary *newUserObject = [NSMutableDictionary dictionary];
    [newUserObject setObject:properties forKey:@"newUser"];

    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:newUserObject options:kNilOptions error:nil];
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
       NSString *urlString = [NSString stringWithFormat:@"http://myPublicIP/MyService/Service1.svc/NewUser"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlString]];
    [request setValue:jsonString forHTTPHeaderField:@"json"];
    [request setHTTPMethod:@"POST"];
    [request setHTTPBody:jsonData];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    NSError *error = nil;
    NSURLResponse *theResponse = [[NSURLResponse alloc]init];
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&theResponse error:&error];
    if(error)
    {
        txtData.text = [error localizedDescription];
    }
    else
    {
        NSMutableString *retVal = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    }

我还测试了在本地主机上运行的/GetUsers方法，该方法总是从users表返回最新的用户列表到web浏览器。问题似乎在服务和客户端之间的某个地方。我是新的网络服务，任何帮助或建议将不胜感激。

[request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];