Bool from viewmodel is not binding in MVC action on a post

Question

I have a view model that has TestStr and TestBool as properties. If I submit the form, only the TestStr value is getting set to the bound view model, but not the TestBool . The value in the form collection for TestBool is set to "on" , is that the issue? Should it be set as true for it to be marked as true?

My c# view model:

public class MyViewModel { 
  public bool TestStr { get; set; }
  public bool TestBool { get; set; }
}

My razor view, inside the form:

<input name="TestStr" value="this is getting set in my MVC action" />
<input name="TestBool" checked=checked /> // this always gets set to false, even tho it's checked

My MVC action:

public ActionResult(MyViewModel vm) {
  // vm.TestBool is always false
}

I notice that if I use the @Html.CheckBoxFor(...) it does correctly bind it in my MVC action. Is it possible to do this using the typed-out html? Only because I have some collections I'm working with, so I'm having to provide the input names for each.

Answer 1

Its because checkboxes don't post back if they are not checked. The HTML helper actually adds a hidden field for the unchecked version, then resolves the conflict (checked / not checked ) correctly.

If you want to preserve other fields, but don't want to display them, Html.HiddenFor can be used to preserve the values.

This post shows someone with the same issue