ReturnUrl is always null on POST using ASP.NET Core 6 MVC

Question

I'm not able to get ReturnUrl to work on HttpPost using ASP.NET Core 6 MVC.

When adding a breakpoint to the POST method, returnurl is always null. But with .NET 5, it works with the same code setup except that with .NET 6, I need to make the returnurl parameter nullable so that I won't get an error "returnurl field is required".

This is the code I'm using - any help would be much appreciated.

Thanks.

Model:

namespace IdentityManagerDotNet6.Models
{
    public class LoginViewModel
    {
        [Required]
        [EmailAddress]
        public string Email { get; set; } = string.Empty;

        [Required]
        [DataType(DataType.Password)]
        public string Password { get; set; } = string.Empty;

        [Display(Name = "Remember me?")]
        public bool RememberMe { get; set; }
    }
}

Controller

[HttpGet]
public IActionResult Login(string? returnurl)
{
    ViewData["ReturnUrl"] = returnurl;
    return View();
}

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Login(LoginViewModel loginViewModel, string? returnurl)
{
    ViewData["ReturnUrl"] = returnurl;
    returnurl = returnurl ?? Url.Content("~/");

    if (ModelState.IsValid)
    {
        var result = await _signInManager.PasswordSignInAsync(loginViewModel.Email, loginViewModel.Password, loginViewModel.RememberMe, lockoutOnFailure: true);

        if (result.Succeeded)
        {
            return LocalRedirect(returnurl);
        }

        if (result.IsLockedOut)
        {
            return View("Lockout");
        }
        else
        {
            ModelState.AddModelError(string.Empty, "Invalid login attempt.");
            return View(loginViewModel);
        }
    }

    return View(loginViewModel);
}

View:

@model LoginViewModel

<h1 class="text-info">Log in</h1>
<div class="row">
    <div class="col-md-8">
        <form asp-controller="Account" asp-action="Login" asp-route-returnurl="@ViewData["ReturnUrl"]" method="post" role="form">
            <h4>Use a local account to log in</h4>
            <hr />
            <div asp-validation-summary="All" class="text-danger"></div>
            <div class="form-group">
                <label asp-for="Email" class="col-md-2"></label>
                <div class="col-md-10">
                    <input asp-for="Email" class="form-control" />
                    <span asp-validation-for="Email" class="text-danger"></span>
                </div>
            </div>
            <div class="form-group mt-3">
                <label asp-for="Password" class="col-md-2"></label>
                <div class="col-md-10">
                    <input asp-for="Password" class="form-control" />
                    <span asp-validation-for="Password" class="text-danger"></span>
                </div>
            </div>
            <div class="form-check mt-3">
                <input class="form-check-input" asp-for="RememberMe" type="checkbox" value="" id="flexCheckChecked">
                <label class="form-check-label" asp-for="RememberMe" for="flexCheckChecked">
                    Remember me?
                </label>
            </div>
            <div class="form-group">
                <div class=" col-1 my-3">
                    <button type="submit" asp-controller="Account" asp-action="Login" class="btn btn-success form-control">Login</button>
                </div>
            </div>
            <p>
                <a asp-action="Register">Register as a new user?</a>
            </p>
            <p>
                <a asp-action="ForgotPassword">Forgot your passord?</a>
            </p>
        </form>
    </div>
</div>

Answer 1

"I'm not able to get ReturnUrl to work on HttpPost using ASP.NET Core 6 MVC.":

I have checked your code between the line. It doesn't has anything wrong with [FromQuery] So you don't need to do anything on [FromQuery] as other answer I've seen, may be deleted now.

Issue Replication:

I have reproduced your issue successfully as you can see below:

What Causing the Issue:

If you investigate your code again you would noticed that you are using asp-controller="Login" asp-action="Login" twice on your Login.cshtml at the begining of the form and at the point of submit button this causing the data loss while you are submitting the form.

At the starting on form:

   <form asp-controller="Login" asp-action="Login" asp-route-returnurl="@ViewData["ReturnUrl"]" method="post" role="form">

At your button submit::

 <button type="submit" asp-controller="Login" asp-action="Login" class="btn btn-success form-control">Login</button>

Solution:

The easiest solution is just modify your submit button code like below which will resolve your issue:

            <div class="form-group">
                <div class=" col-1 my-3">
                    <button type="submit" class="btn btn-success form-control">Login</button>
                </div>
            </div>

Output:

Hope it will resolve your returnurl null issue completely.