如何在ASP.NET MVC中的页面之间正确发布值？

Question

For love nor money I can't understand the magic mapping that ASP.NET MVC performs when I post values between pages.

I have a "wizard" consisting of 3 controller actions: NewRequest, NewRequestValidation and PostNewRequest. NewRequest collects some form input and passes it to NewRequestValidation where the user confirms their request and either submits it to PostNewRequest or rejects it and returns to NewRequest.

NewRequest uses:

@model SCL.Intranet.Controllers.HR.LeaveRequests.NewLeaveRequestViewModel

NewRequestValidation expects the NewLeaveRequestViewModel as a parameter on the method signature:

public ActionResult NewRequestValidation(NewLeaveRequestViewModel lrvm)

It then does some validation and passes a NewLeaveRequestAnalysisViewModel down to the corresponding View.

The NewRequestValidation view uses:

@model SCL.Intranet.Controllers.HR.LeaveRequests.NewLeaveRequestAnalysisViewModel

I am trying to post some parts of the NewLeaveRequestAnalysisViewModel, specifically the "NewLeaveRequestViewModel" part into PostNewRequest.

My form definition, including some hidden fields to transport the appropriate values, looks like:

@using (Html.BeginForm("PostNewRequest", "LeaveRequests", new { area = "HR" }, FormMethod.Post, new { @class = "form-horizontal" }))
 {
  @Html.HiddenFor(m => m.NewLeaveRequest)
  @Html.HiddenFor(m => m.NewLeaveRequest.From.Date)
  @Html.HiddenFor(m => m.NewLeaveRequest.From.Half)
  @Html.HiddenFor(m => m.NewLeaveRequest.Until.Date)
  @Html.HiddenFor(m => m.NewLeaveRequest.Until.Half)
  @Html.HiddenFor(m => m.NewLeaveRequest.Type.LeaveRequestTypeId)

  // Some presentation stuff here.
}

Finally, PostNewRequest expects a NewLeaveRequestViewModel:

public ActionResult PostNewRequest(NewLeaveRequestViewModel lrvm)

I understand that I need to pass a NewLeaveRequestViewModel in, and that my current code doesn't work because I'm actually just passing in a bunch of fields that happen to have their values from a previous instance of NewLeaveRequestViewModel.

The question is: How do I set up a new NewLeaveRequestViewModel in NewRequestValidation that will match the signature on PostNewRequest?

Answer 1

I fixed this by using TempData as suggested (I think!) by meda.

In the "NewRequestValidation" action, I commit the NewLeaveRequestViewModel to TempData:

TempData.Add("PendingLeaveRequest", lrvm);

Then, in PostNewRequest, I get it back out of TempData again:

if (TempData.ContainsKey("PendingLeaveRequest"))
{
  var lrvm = TempData["PendingLeaveRequest"] as NewLeaveRequestViewModel;
  // Do something with lrvm
}