Using hidden fields during HTTP post for the reload of same page postback

Question

I have a View where the User can leave a feedback comment in regards to the content video that is playing on the page. Using the following code I am able to manually enter the UserID and ContentID and it saves to the database without problem.

@using (Html.BeginForm("Screencast", "Media", FormMethod.Post, new { id = "form", enctype = "multipart/form-data" }))
        {              
          <div class="row">
            <div class="six columns">
              <div class="row">
                <div class="six columns">
                  @Html.LabelFor(c => c.FeedbackComment.UserID)
                  @Html.TextBoxFor(c => c.FeedbackComment.UserID)
                </div>
                <div class="six columns">
                  @Html.LabelFor(c => c.FeedbackComment.ContentID)
                  @Html.TextBoxFor(c => c.FeedbackComment.ContentID)
                </div>   
                <div class="row">
                  <div class="twelve columns">
                    @Html.LabelFor(c => c.FeedbackComment.FeedbackString)
                    @Html.TextAreaFor(c => c.FeedbackComment.FeedbackString)
                  </div>
                </div>        
              </div>
            </div>
          </div>          
          <input type="submit" value="Submit button" class="medium button bottom20"/>
        }

However, when the user is on the page before the HTTP post I actually have the related variables in my Model called:

Model.User.UserID
Model.SelectedItem.ContentID

I want to pass these in as hidden fields but when I try to do either:

@HtmlHiddenFor(c => c.FeedbackComment.UserID, @Model.User.UserID)
@HtmlHiddenFor(c => c.FeedbackComment.ContentID, @Model.SelectedItem.ContentID)

or

@HtmlHidden("UserID",@Model.User.UserID)
@HtmlHidden("ContentID",@Model.User.UserID)

Then these values are returned null despite the values being populated before the post. I read about a workaround of putting the input tags in manually but when I did this the @Using.HtmlBeginForm was returning an error of not being set to an instance of an object

Can someone please help me to understand how I can pass these values to the same page using the values I have in the model prior to the post.

Answer 1

Given the following view model (partial):

public class YourViewModel
{
     public User User { get; set; }

     public SelectedItem SelectedItem { get; set; }
}

You can bind the these properties to a hidden form element. When you post back these properties will still contain their values.

@Html.HiddenFor(x => x.User.UserID)
@Html.HiddenFor(x => x.SelectedItem.ContentID)

Your action method:

public ActionResult YourActionMethod(YourViewModel viewModel)
{
     // When you debug here you will see that the values are retained
}

I hope this helps.