ASP.NET Core ViewData, BindProperty or TempData?

Question

In ASP.NET Core Views and Razor Pages we can use:

public class LoginModel
{
    [BindProperty]
    public bool DisplayCaptcha { get; set; }

    // OR

    [ViewData]
    public bool DisplayCaptcha { get; set; }

    // OR

    [TempData]
    public bool DisplayCaptcha { get; set; }
}

To share data between View/Page/Controller... But when to use each one?

In my case its a simple login page and when user set a wrong password I will display a captcha.

In the form post i'm setting a property to true (DisplayCaptcha = true) and rendering the page with the captcha:

@if (Model.DisplayCaptcha)
{            
    <div class="captcha-header">
        ...
    </div>
}

This is working fine but i'm little confuse what type the attribute should be or even if I should use any.

Answer 1

ViewData should be used when data is passed from PageModel to Page.

BindProperty should be used when data is passed from PageModel to Page and vice versa via POST/GET. This is two-way binding.

TempData should be used when data should be read only once.

In your case you should use BindProperty.