I am a beginner to ASP.NET MVC coding using C#, and during one of the learning sessions I was implementing relationship between 2 SQL Server tables using Entity Framework.

However, when I tried running it on localhost, I got this error:

System.InvalidCastException
HResult=0x80004002
Message=Unable to cast object of type 'Dev.DB.SUST_INC_TRCKR_DTLS' to type 'System.Collections.Generic.ICollection`1[Dev.DB.SUST_INC_TRCKR_DTLS]'.
Source=Dev.DB

StackTrace:

at Dev.DB.DBOperations.SustHCRepository.Onboard_Sust_HC(HC_TBL hc) in C:\Users\NT_ID\source\repos\Training\Dev.DB\DBOperations\SustHCRepository.cs:line 32
at MVC_Lesson13.Controllers.CreateController.Index(HC_TBL hc) in C:\Users\NT_ID\source\repos\Training\MVC_Lesson13\Controllers\CreateController.cs:line 30
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult, ActionInvocation innerInvokeState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_0.b__0() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.b__2()

Below are the both the classes I am using with entity .tt classes.

Primary key table's model class:

enter image description here

Foreign key table's model class:

enter image description here

Entity .tt C# for primary key table:

enter image description here

Entity .tt C# for foreign key table:

enter image description here

Database operations repository C# (this where I get the error):

enter image description here

I surely know for a fact that I am making some mistake. However, none of the google or stack forums could provide the solution on this.

Please help

CodePudding user response：

Next time pls post the code instead of pics or your post will be closed.

But because of New Year holiday, fix the line where is the error message , it should be

SYST_IC_TRCKR_DTLS= new List<SYST_INC_TRCKR_DTLS> {SYST_INC_TRCKR}