asp.net core razor page checkboxes model binding (always false)

Question

User1653152239 posted

i have a razor page in asp.net core with the following input tag:

<input asp-for="chkPref" />

in the code-behind i have:

public bool chkPref { get; set; }

so when i run the app, i can confirm in `Request.Form` that I'm getting...

checkbox checked = {true,false}

checkbox unchecked = {false}

which is expected, according to https://www.learnrazorpages.com/razor-pages/forms/checkboxes

however, that page states that the model binding will figure out that `{true,false}` is actually `true` but i'm getting `false` no matter what.

the website above alludes to the fact that this "just happens"...

If the checkbox is checked, the posted value will be true,false. The model binder will correctly extract true from the value. Otherwise it will be false.

but that doesn't seem to be working, or at least isn't that obvious how it works.

Answer 1

User475983607 posted

Works for me.  Demo code follows.

@page
@model RazorDemo.Pages.general.CheckDemoModel
@{
    ViewData["Title"] = "CheckDemo";
}

<h1>CheckDemo</h1>

<form method="post">
    <input asp-for="chkPref" />
    <input id="Submit1" type="submit" value="submit" />
</form>
<div>
    @Model.Message
</div>

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace RazorDemo.Pages.general
{
    public class CheckDemoModel : PageModel
    {
        [BindProperty]
        public bool chkPref { get; set; }
        public string Message { get; set; } = string.Empty;
        public void OnGet()
        {

        }

        public void OnPost()
        {
            Message = $"The value is {chkPref}";
        }
    }
}

Answer 2

User1653152239 posted

problem was i was missing this...

[BindProperty]

as stated on this page...

https://www.learnrazorpages.com/razor-pages/forms#handler-method-parameters

The property to be included in model binding must be decorated with the BindProperty attribute.

Thanks!