使用ASP.NET MVC 5更改请求后，如何在控制器中手动验证模型？

Question

In have an application that is written on the top on the ASP.NET MVC 5 framework.

I have a page with two separate forms (one visible and the other hidden when the page is loaded). The first form has a drop down menu, if the user selects the option "ABC", I use javascript do display the second form. But if he/she selects any other option, I hide the second form.

Using javascript, I change the required property for the required field to optional since the form is not visible. (this is done only to the client side only)

Now, since the second form has some required fields at the server side, every time I submit the form, the property ModelState.IsValid is always false because the second form has some required field which is not provided.

Somehow, before I validate the form, I need to alter the model by setting the SecondForm property to null then validate.

Here is how my ViewModelCapsule class look like

public class ViewModelCapsule
{
    public FirstFormViewModel FirstForm { get; set; }
    public SecondFormViewModel SecondForm { get; set; }
}

I tried to work around this issue by using TryValidateModel() method on my controller like so

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Update(int id, ViewModelCapsule model)
{
    try
    {

        if(model.FirstModel != null && model.FirstModel.Menu1 != "ABC")
        {
            model.SecondModel = null
        }

        if (TryValidateModel(model))
        {
            // Here I am expecting the form to validate since the first form has valid date
            // Do somethig with the request

        }

        return new RedirectAction("Index");

    }
    catch (Exception exception)
    {
        return Content(exception.Message);
    }
}

but for some reason TryValidateModel(model) is also returning false. I evaluated the incoming data and FirstForm has correct data in all of its properties.

How can I manually validate a model in the controller after altering the request?

Answer 1

I believe I got it to work now. I had to add this line of code to my controller

ModelState.Clear();

My controller looks like this

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Update(int id, ViewModelCapsule model)
{
    try
    {

        if(model.FirstModel != null && model.FirstModel.Menu1 != "ABC")
        {
            ModelState.Clear();
            model.SecondModel = null

        }

        if (TryValidateModel(model))
        {
            // Here I am expecting the form to validate since the first form has valid date
            // Do somethig with the request

        }

        return new RedirectAction("Index");

    }
    catch (Exception exception)
    {
        return Content(exception.Message);
    }
}