MVC3 Child Action breaking my DateTime Editor Template - asp.net-mvc-3

Question

I have a generic DateTime editor template that should format all of my DateTime properties with the required format("dd/MM/yyyy"):
#Html.TextBox(string.Empty, Model.ToString("dd/MM/yyyy"), new { #class = "datepicker" })
but for some reason the format is not working for my child actions.
If I do #Html.EditorFor(x => x.MyDate) in MainPage.cshtml
I get the expected result of: "23/04/2012"
If I do #Html.EditorFor(x => x.MyDate) in ChildAction.cshtml
I get the unexpected result of: "2012-04-24"
I can confirm that the Editor Template is being used, because if I change it like so (notice the WTF string at the beginning):
WTF #Html.TextBox(string.Empty, Model.ToString("dd/MM/yyyy"), new { #class = "datepicker" })
Then if I do #Html.EditorFor(x => x.MyDate) in ChildAction.cshtml
I get: "WTF 2012-04-24"
Any ideas?
Update
In my quest to reproduce this error in the MVC sample app, I found that two other things are required:
public class DateTimeModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
DateTime date;
if (DateTime.TryParseExact(value.AttemptedValue, "dd/MM/yyyy", DateTimeFormatInfo.CurrentInfo, DateTimeStyles.AssumeLocal, out date))
{
return date;
}
return base.BindModel(controllerContext, bindingContext);
}
}
I'm assuming everyone knows how to wire that up. Also in the MainPage.cshtml you must pass the model in as the second parameter to RenderAction
#{Html.RenderAction("Child", Model);}
When passing the model as the second parameter, MVC uses the model binder to call the child action (why?). However, the format of the date is MM/dd/yyyy so it doesn't work with my model binder which assumes all my dates will be in dd/MM/yyyy format. That's why this isn't working.
But how do I fix it? The only place where the dates don't match my default format of dd/MM/yyyy is when rendering a child action.

Answer 1

The problem
MVC uses modelstate values if possible but the values are different in the model state of the parent action vs the child action:
In the parent action, the model state contains a string for the date submitted to the action (RawValue in the valueproviderresult) or a default value.
When the parent action passes the information to the child action
(renderaction) it passes a dateTime in the model state (RawValue in
the valueproviderresult).
So in the parent action, if no value is submitted, the value provided in Textbox(...) is correctly used. If a valid value is submitted by the client in the same format, it appears to be ok too since it takes the string in the model state which is identical to the one generated in the displaytemplate.
But in the child action it uses the modelstate which contains a datetime instead of the submitted string, MVC then convert that datetime to a string using invariantculture so it will show MM/dd/yyyy (I'm 3 years later so the value may have changed in the framework since you are having yyyy-MM-dd)
The solution
You need to replace the values in the model state with what you want or remove it for the affected values.
public static void Fix(ModelStateDictionary dic, string key)
{
ModelState modelState = dic[key];
if (!modelState.Errors.Any() && modelState.Value.RawValue != null
&& (modelState.Value.RawValue is DateTime || modelState.Value.RawValue is DateTime?))
{
var sValue = ((DateTime)modelState.Value.RawValue).ToString("dd/MM/yyyy");
var value = new ValueProviderResult(sValue, sValue, CultureInfo.InvariantCulture);
dic.SetModelValue(key, value);
//or
//dic.Remove(key);
}
}
and then call that method in your child action:
Fix(ModelState, nameof(viewModel.DateMax));