MVC DisplayFor function - how do I find out which template is used?

Question

I have the following problem:

@Html.DisplayFor(m => m.PkID)

(where PkID is of type long) fails with the following exception:

[InvalidOperationException: The model item passed into the dictionary is of type 'System.Int64', but this dictionary requires a model item of type 'System.String'.]
   System.Web.Mvc.ViewDataDictionary`1.SetModel(Object value) +378
   System.Web.Mvc.ViewDataDictionary.set_Model(Object value) +47
   System.Web.Mvc.ViewDataDictionary..ctor(ViewDataDictionary dictionary) +614
   System.Web.Mvc.ViewDataDictionary`1..ctor(ViewDataDictionary viewDataDictionary) +37
   System.Web.Mvc.WebViewPage`1.SetViewData(ViewDataDictionary viewData) +98
   System.Web.Mvc.WebViewPage.set_ViewData(ViewDataDictionary value) +39
   System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +425
   System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +382
   System.Web.Mvc.Html.TemplateHelpers.ExecuteTemplate(HtmlHelper html, ViewDataDictionary viewData, String templateName, DataBoundControlMode mode, GetViewNamesDelegate getViewNames, GetDefaultActionsDelegate getDefaultActions) +1037
   System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData, ExecuteTemplateDelegate executeTemplate) +1621
   System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData) +94
   System.Web.Mvc.Html.TemplateHelpers.TemplateFor(HtmlHelper`1 html, Expression`1 expression, String templateName, String htmlFieldName, DataBoundControlMode mode, Object additionalViewData, TemplateHelperDelegate templateHelper) +225
   System.Web.Mvc.Html.TemplateHelpers.TemplateFor(HtmlHelper`1 html, Expression`1 expression, String templateName, String htmlFieldName, DataBoundControlMode mode, Object additionalViewData) +140
   System.Web.Mvc.Html.DisplayExtensions.DisplayFor(HtmlHelper`1 html, Expression`1 expression) +92

We have lots of DisplayTemplates and EditorTemplates in our project and I am certain that one of them is used instead of the default, but I need to know which template is chosen (incorrectly) so that I can fix the content.

How do I find out which template was chosen by the framework? Using the call stack in Visual Studio 2013 didn't help because I only get decompiled Assembler code for the method that would have the template name (System.Web.Mvc.Html.TemplateHelpers.ExecuteTemplate).

Answer 1

In Visual Studio, go to Tools > Options > Debugging and uncheck Step over properties and operators (Managed Only)

Then add a breakpoint on @Html.DisplayFor(m => m.PkID) . It will probably step into lots of other stuff but will eventually end up in the template

Answer 2

For me, the best way to determine which template is executed is to know how display and editor templates are handled in MVC framework. There are just a few different options you should check

• You explicitly specified template name in DisplayFor call (which is not the option in your case)
• You used UIHintAttribute on PkID to instruct framework which template to use
• You have template under Views/ControllerName/DisplayTemplates
• You have template placed under Views/Shared/DisplayTemplates

Note that even if template is placed on plysical location but excluded from visual studio solution, it will still be rendered.