CODEWITHSUNDEEP
asp.netasp.net-mvcasp.net-mvc-4lambdaobject-reference
Igor Entaltsev
Igor Entaltsev

Reputation: 67

ASP.NET MVC4 lambda expression error - Object reference not set to an instance of an object

I keep getting this error in line 146. I would appreciate anybody explaining this error to me.

Server Error in '/' Application.

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

Line 144:            var courses = dc.Courses.ToList().  
Line 145:                Where(course =>  
Line 146:                    course.   <------??????
Line 147:                    User. 
Line 148:                    Id ==   
Line 149:                    currentUserId);

Source File: c:\aaa\vat\c#\proj\igoryen\igoryen\ViewModels\Repo_Course.cs Line: 146

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   igoryen.ViewModels.<>c__DisplayClassb.<getListOfCourseBaseAM>b__a(Course course) in c:\aaa\vat\c#\proj\igoryen\igoryen\ViewModels\Repo_Course.cs:146
   System.Linq.WhereListIterator`1.MoveNext() +56
   System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +381
   System.Linq.Enumerable.ToList(IEnumerable`1 source) +58
   AutoMapper.Mappers.EnumerableMapperBase`1.Map(ResolutionContext context, IMappingEngineRunner mapper) +273
   AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) +838

[AutoMapperMappingException: 

Mapping types:
WhereListIterator`1 -> IEnumerable`1
System.Linq.Enumerable+WhereListIterator`1[[igoryen.Models.Course, igoryen, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] -> System.Collections.Generic.IEnumerable`1[[igoryen.ViewModels.CourseBase, igoryen, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]

Destination path:
IEnumerable`1

Source value:
System.Linq.Enumerable+WhereListIterator`1[igoryen.Models.Course]]
   AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) +936
   AutoMapper.MappingEngine.Map(Object source, Type sourceType, Type destinationType, Action`1 opts) +196
   AutoMapper.MappingEngine.Map(Object source, Action`1 opts) +172
   AutoMapper.MappingEngine.Map(Object source) +121
   AutoMapper.Mapper.Map(Object source) +107
   igoryen.ViewModels.Repo_Course.getListOfCourseBaseAM(String currentUserId) in c:\aaa\vat\c#\proj\igoryen\igoryen\ViewModels\Repo_Course.cs:151
   igoryen.ViewModels.Repo_Course.getSelectListOfCourse(String currentUserId) in c:\aaa\vat\c#\proj\igoryen\igoryen\ViewModels\Repo_Course.cs:136
   igoryen.Controllers.CancellationsController.Create() in c:\aaa\vat\c#\proj\igoryen\igoryen\Controllers\CancellationsController.cs:50
   lambda_method(Closure , ControllerBase , Object[] ) +101
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +59
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +435
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +60
   System.Web.Mvc.Async.ActionInvocation.InvokeSynchronousActionMethod() +76
   System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__36(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +36
   System.Web.Mvc.Async.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) +73
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +136
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +49
   System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3c() +117
   System.Web.Mvc.Async.<>c__DisplayClass45.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3e() +323
   System.Web.Mvc.Async.<>c__DisplayClass30.<BeginInvokeActionMethodWithFilters>b__2f(IAsyncResult asyncResult) +44
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +47
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +136
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +50
   System.Web.Mvc.Async.<>c__DisplayClass28.<BeginInvokeAction>b__19() +72
   System.Web.Mvc.Async.<>c__DisplayClass1e.<BeginInvokeAction>b__1b(IAsyncResult asyncResult) +185
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +133
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +40
   System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +34
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +70
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +139
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +44
   System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +39
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +62
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +139
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +39
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +39
   System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__4(IAsyncResult asyncResult, ProcessRequestState innerState) +39
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +70
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +139
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +40
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9514928
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.18446

Update 1

Well this is what I have for user: 

// 1) Peter teaches IPC144
Course c = new Course();  
c.CourseCode = "IPC144";  
c.CourseName = "Introduction into programming";  
c.RoomNumber = "1000";      
c.RunTime = "1000";  
c.Faculty = f;  
c.User = UserPeter; // 17  
f.Courses.Add(c); //  
c.Students.Add(bob);  
bob.Courses.Add(c);  
dc.Courses.Add(c);  
c = null;

Update 2

Unfortunately, I can't post a screen shot here, but I am debugging with a breakpoint and I don't see any User values that are null .

Update 3

I have these files:

The part I am not getting is this:
as I debug with breakpoints I see that:

Update 4

UserPeter is of type ApplicationUser:

var UserPeter = new ApplicationUser();
string userPw8 = "123456";
var userInfo8 = new MyUserInfo() { FirstName = "Peter", LastName = "Peterson" };
UserPeter.UserName = "Peter";
UserPeter.HomeTown = "Toronto";
UserPeter.MyUserInfo = userInfo8;
var UserPeterCreate = UserManager.Create(UserPeter, userPw8);
if (UserPeterCreate.Succeeded) {
    var addUserPeterToRole3Result = UserManager.AddToRole(UserPeter.Id, roleName3);
}

The ApplicationUser class, it derives from IdentityUser: 

public class ApplicationUser : IdentityUser {
    //[Key]
    //public int Id { get; set; }
    public string HomeTown { get; set; } 
    //public virtual ICollection<Cancellation> Cancellations { get; set; }
    //public virtual ICollection<Course> Courses { get; set; }
    public virtual MyUserInfo MyUserInfo { get; set; }
}

The MyUserInfo class

public class MyUserInfo {
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

The IdentityUserclass (from metadata):

public class IdentityUser : IUser {
    public IdentityUser();
    public IdentityUser(string userName);

    public virtual ICollection<IdentityUserClaim> Claims { get; }
    public virtual string Id { get; set; }
    public virtual ICollection<IdentityUserLogin> Logins { get; }
    public virtual string PasswordHash { get; set; }
    public virtual ICollection<IdentityUserRole> Roles { get; }
    public virtual string SecurityStamp { get; set; }
    public virtual string UserName { get; set; }
}

The Course class: 

public class Course { // 10
  public Course() {
    this.Faculty = new Faculty();
    this.Students = new List<Student>();
  }
  [Key]
  public int CourseId { get; set; }
  public string CourseCode { get; set; }
  public string CourseName { get; set; }
  public string RoomNumber { get; set; }
  public string RunTime { get; set; }
  public Faculty Faculty { get; set; }
  public List<Student> Students { get; set; }
  public virtual ApplicationUser User { get; set; }
}

Upvotes: 1

Views: 2816

Answers (2)

Wormbo
Wormbo

Reputation: 4992

If line 146 does the null access, it's more likely that your courses list contains null values than some course having a null user.

Upvotes: 0

Andrew Lewis
Andrew Lewis

Reputation: 5256

One of the values in the list for your User object is null.

Upvotes: 1

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