MVC using VS: Why am I getting an error when using View() but not when I use View(viewname)? - model-view-controller

Question

I am getting a strange error when using the following:
public ActionResult PostToPayPal(WalkerRegoViewModel walkerVM, string submit)
...
return View(paypal);
But when I specify the ViewName it works (nothing else has changed)?
public ActionResult PostToPayPal(WalkerRegoViewModel walkerVM, string submit)
...
return View("PostToPayPal", paypal);
The error I get is:
Object reference not set to an instance of an object.
Exception Details:
System.NullReferenceException: Object reference not set to an instance of an object.
Here is the Stack Trace:
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:
An unhandled exception was generated during the execution cf the current web request. Information regarding the origin and locaticn of the exception can be identified using the exception stack trace below.
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
Walk.Controllers.RegisterController.PostToPayPal(WalkerRegoViewModel walkerVM, String submit) in C:\dev\Walk\Walk\Controllers\RegisterController
lambda_method(Closure , ControllerBase , Object[] ) +147
System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +14
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary.2 parameters) +169
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary-2
System.Web.Mvc.Async.oc.b 9_0(IAsyncResult asyncResult, Actionlnvocation innerInvokeState) +22
System.Web.Mvc.Async.WrappedAsyncResult.2.CallEndDelegate(IAsyncResult asyncResult) +29
System.Web.Mvc.Async.WrappedAsyncResultBase.1.End() +49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +32
System.Web.Mvc.Async.oc DisplayClass11_0.b 0() +58
System.Web.Mvc.Async.oc DisplayClass11_2.b 2() +228
System.Web.Mvc.Async.oc DisplayClass7_0.b 1(IAsyncResult asyncResult) +10
System.Web.Mvc.Async.WrappedAsyncResult.1.CallEndDelegate(IAsyncResult asyncResult) +10
System.Web.Mvc.Async.WrappedAsyncResultBase.1.End() +49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +34
System.Web.Mvc.Async.oc DisplayClass3_6.b 4() +35
System.Web.Mvc.Async.oc DisplayClass3_1.b 1(IAsyncResult asyncResult) +100
System.Web.Mvc.Async.WrappedAsyncResult.1.CallEndDelegate(IAsyncResult asyncResult) +10
System.Web.Mvc.Async.WrappedAsyncResultBase.1.End() +49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
System.Web.Mvc.oc.b 152_1(IAsyncResult asyncResult, ExecuteCoreState innerState) +11
System.Web.Mvc.Async.WrappedAsyncVoid.1.CallEndDelegate(IAsyncResult asyncResult) +29
System.Web.Mvc.Async.WrappedAsyncResultBase.1.End() +49
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +45
System.Web.Mvc.oc.b 151_2(IAsyncResult asyncResult, Controller controller) +13
System.Web.Mvc.Async.WrappedAsyncVoid.1.CallEndDelegate(IAsyncResult asyncResult) +22
System.Web.Mvc.Async.WrappedAsyncResultBase.1.End() +49