Exception at initialization of DateTime

Question

I am initialiting DateTime variable in the parameters of a controller action as below

public ActionResult ForFahrzeug(DateTime initDat = default(DateTime), long id = 0, long   
                             days = 0, string ExpGnr = "")
    {
        //body
    }

There is no error at compile time but an exception occurred during runtime.

Server Error in '/' Application.
Encountered an invalid type for a default value.
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.FormatException: Encountered an invalid type for a default value.

Stack Trace:

[FormatException: Encountered an invalid type for a default value.]
System.Reflection.MdConstant.GetValue(MetadataImport scope, Int32 token, RuntimeTypeHandle   fieldTypeHandle, Boolean raw) +10764128
System.Reflection.RuntimeParameterInfo.GetDefaultValueInternal(Boolean raw) +413
System.Reflection.RuntimeParameterInfo.GetDefaultValue(Boolean raw) +31
System.Reflection.RuntimeParameterInfo.get_DefaultValue() +6
System.Web.Mvc.ParameterInfoUtil.TryGetDefaultValue(ParameterInfo parameterInfo, Object& value) +64
System.Web.Mvc.ReflectedParameterDescriptor.get_DefaultValue() +59
System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +541
System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +199
System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState) +978
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +161
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +92
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag) +53
System.Web.Mvc.Async.AsyncControllerActionInvoker.BeginInvokeAction(ControllerContext controllerContext, String actionName, AsyncCallback callback, Object state) +538
System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__17(AsyncCallback asyncCallback, Object asyncState) +83
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +161
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +92
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag, Int32 timeout) +97
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag) +53
System.Web.Mvc.Controller.BeginExecuteCore(AsyncCallback callback, Object state) +531
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +161
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +92
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag, Int32 timeout) +97
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag) +53
System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +447
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +49
System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__2(AsyncCallback asyncCallback, Object asyncState) +127
System.Web.Mvc.Async.WrappedAsyncResult`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +161
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +92 
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag, Int32 timeout) +97
System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag) +53
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +388
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +88
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +50
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +301
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Answer 1

This behavior is reported here: https://connect.microsoft.com/VisualStudio/feedback/details/733995/datetime-default-parameter-value-throws-formatexception-at-runtime

Seems to be a bug.

You can optionally do it like this:

 public ActionResult ForFahrzeug(DateTime? initDat = null, ...
 {
 }