Questions Initial REST Setup

Alright, got it working! I was passing it as text instead of JSON.

On to part 2. I can get the sales order info with the following get -

https://thomson.nellnube.com/HTSLabs/entity/default/6.00.001/SalesOrder?$top=5

But if I try for detail, with this get - 

https://thomson.nellnube.com/HTSLabs/entity/default/6.00.001/SalesOrder?$top=5&$expand=SalesOrderDetail

Postman errors on me - 

"message": "An error has occurred.",
"exceptionMessage": "The given key was not present in the dictionary.",
"exceptionType": "System.Collections.Generic.KeyNotFoundException",

I was reading through I210, but it's light on REST documentation. What are your thoughts? 

Full error txt:

{
"message": "An error has occurred.",
"exceptionMessage": "The given key was not present in the dictionary.",
"exceptionType": "System.Collections.Generic.KeyNotFoundException",
"stackTrace": " at System.ThrowHelper.ThrowKeyNotFoundException()\r\n at System.Collections.Generic.Dictionary`2.get_Item(TKey key)\r\n at Microsoft.Data.OData.Query.SyntacticAst.ExpandBinder.GenerateExpandItem(ExpandTermToken tokenIn)\r\n at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()\r\n at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()\r\n at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)\r\n at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)\r\n at Microsoft.Data.OData.Query.SyntacticAst.ExpandBinder.Bind(ExpandToken tokenIn)\r\n at Microsoft.Data.OData.Query.SelectExpandSemanticBinder.Parse(IEdmEntityType elementType, IEdmEntitySet entitySet, ExpandToken expandToken, SelectToken selectToken, ODataUriParserConfiguration configuration)\r\n at PX.Api.ContractBased.OData.Helpers.ParseSelectCustomAndExpand(ODataUriParser uriParser, String select, String expand, String custom, IEdmEntityType elementType, EntityImpl entity, Nullable`1 returnBehaviorToSet)\r\n at PX.Api.ContractBased.OData.Helpers.FillRestQueryOptions(IEdmModel edmModel, EntityImpl entity, String filter, String select, String expand, String custom)\r\n at PX.Api.ContractBased.SystemContracts.V2.RestController.GetList(String objectName, String select, String filter, String expand, String custom, Nullable`1 skip, Nullable`1 top)\r\n at lambda_method(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"