[Solved] Upload tool for ASP.NET MVC on Postback

[Andrew]

I am currently using the upload tool for ASP.NET MVC, and am having a small issue. Part of the logic when the page posts is to make sure that a file exists and that the user has input a name for the record. If there is no name entered, the model state become invalid and the view is reloaded with the information from the model. My problem is, if you select a file to upload, forget to enter a name, then submit the form, the validation fails and sends you back to the page as it should, but the list of attachments to upload is not retained. Is there any way I can retain these attachments and pass them back to the view if the model is invalid? 

[T. Tsonev]

Hi Andrew,

The list of uploaded files can't be retained between requests. What you can do is to store the file in a temporary location and use it on the next form submit. The temporary location can be transferred between views using TempData.

We can try to provide a detailed suggestion if you share more details about your scenario.

I hope this helps.

Best Regards,
Tsvetomir Tsonev
the Telerik team

[Andrew]

Thanks for your quick response!

Basically what I have going on is this: There is a "Create Process" page, which allows a user to create a process consisting of a name (string), description (string), and a file. The name and file are both required attributes of a process. If a user selects a file to upload, but fails to enter a name, the validation will fail (as name is required). When the validation fails, the view is reloaded, but the file that they attached is lost. The code below is what happens when the create view posts:

[HttpPost]
public ActionResult Create(EditProcessViewModel processToCreate, IEnumerable<HttpPostedFileBase> attachments)
{
    //Make sure the user selected a file to upload
    if (attachments == null)
    {
        ModelState.AddModelError("path", "You must select a file to upload");
    }

    //If the model is not valid, reload the page with the appropriate errors
    if (!ModelState.IsValid)
    {
        return View(processToCreate);
    }
    else
    {
        //Code to save the uploaded file and persist the process to the database
    }
}

Basically what I want to happen is not only preserve the "EditProcessViewModel", but the file that the user chose to upload as well, so that when the user is returned to the view because of a failed validation, the file they chose is still in the attachments list.

[Atanas Korchev]

Hello Andrew, 

It seems that the previous suggestion is the only possible way:

1. Always save the uploaded files 
2. Store the location (path) of the saved files in TempData or Session
3. If validation fails show the user the uploaded files - you can even hide the upload if there are any uploaded files stored in TempData

Regards,
Atanas Korchev
the Telerik team