How to pass class via RedirectToAction

问题:

I have the following code:

    public ActionResult Index()
    {
        AdminPreRegUploadModel model = new AdminPreRegUploadModel()
        {
            SuccessCount = successAddedCount,
            FailureCount = failedAddedCount,
            AddedFailure = addedFailure,
            AddedSuccess = addedSuccess
        };
        return RedirectToAction("PreRegExceUpload", new { model = model });
    }

    public ActionResult PreRegExceUpload(AdminPreRegUploadModel model)
    {
        return View(model);
    }

but model is null when I breakpoint on PreRegExcelUpload. Why?

回答1:

Instead of using the Session object in Evgeny Levin's answer I would suggest to use TempData. See http://rachelappel.com/when-to-use-viewbag-viewdata-or-tempdata-in-asp.net-mvc-3-applications about TempData.

You could also fix this by calling return PreRegExceUpload(model); instead of return RedirectToAction(..) in you Index function.

回答2:

TempData is just a "smart" wrapper for the Session, under the hood it still acts the same way.

Since it's only 4 fields, i would pass them via querystring.

Always try and avoid session/tempdata where possible, for which in this scenario it certainly is.

Are you sure that's your full code? As it doesn't make sense.

If your POST'ing some data and saving it to the database (for example), usually you redirect to another action passing the unique identifier (which is usually generated after the save), fetch it back from the DB and return the view.

That is much better practice.

If you explain your scenario a bit more, and show the proper code your using, i can help further.

回答3:

Use session to pass model to method:

public ActionResult Index()
{
    AdminPreRegUploadModel model = new AdminPreRegUploadModel()
    {
        SuccessCount = successAddedCount,
        FailureCount = failedAddedCount,
        AddedFailure = addedFailure,
        AddedSuccess = addedSuccess
    };
    Session["someKey"] = model;
    return RedirectToAction("PreRegExceUpload");
}

public ActionResult PreRegExceUpload()
{
    var model = (AdminPreRegUploadModel) Session["someKey"];
    Session["someKey"] = null;
    return View(model);
}

Method RedirectToAction() can't take non primitive types as parameters, because url parameters is string.