Server Error in '/' Application.

A relationship multiplicity constraint violation occurred: An EntityReference expected at least one related object, but the query returned no related objects from the data store.

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.InvalidOperationException: A relationship multiplicity constraint violation occurred: An EntityReference expected at least one related object, but the query returned no related objects from the data store.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[InvalidOperationException: A relationship multiplicity constraint violation occurred: An EntityReference expected at least one related object, but the query returned no related objects from the data store.]
   System.Data.Objects.DataClasses.EntityReference`1.Load(MergeOption mergeOption) +688
   Firelab.Core.DBEngine.Save(Apteka7yaContext context, String callMethod) +822
   Firelab.Core.DBEngine.AddProductInOrder(Guid orderId, Guid productId) +2777
   WebApp.Cart.AddProductInCart(Guid productId) +478
   WebApp.Cart.Page_Load(Object sender, EventArgs e) +572
   System.Web.UI.Control.OnLoad(EventArgs e) +106
   System.Web.UI.Control.LoadRecursive() +68
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3785


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.7.3930.0