如何解决错误 CS1525 Invalid expression term '='？

Question

This is the code of the post method in the register class :

    public async Task<IActionResult> OnPostAsync(string returnUrl = null)
    {
       returnUrl ??= Url.Content("~/Account/feeds");
        ExternalLogins = (await _signInManager.GetExternalAuthenticationSchemesAsync()).ToList();
        if (ModelState.IsValid)
        {

            var user = new ApplicationUser { 
                UserName = Input.username,
                Email = Input.Email,
                DateOfBirth = Input.DOB,
                Gender = Input.Gender
            };
            //this one too

            //notice ma3aml dbcontext.add(user) batteekh w 3amal save..
            var result = await _userManager.CreateAsync(user, Input.Password);
            if (result.Succeeded)
            {
                _logger.LogInformation("User created a new account with password.");

                /*var code = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                code = WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(code));
                var callbackUrl = Url.Page(
                    "/Account/ConfirmEmail",
                    pageHandler: null,
                    values: new { area = "Identity", userId = user.Id, code = code },
                    protocol: Request.Scheme);

                await _emailSender.SendEmailAsync(Input.Email, "Confirm your email",
                    $"Please confirm your account by <a href='{HtmlEncoder.Default.Encode(callbackUrl)}'>clicking here</a>.");*/

                if (_userManager.Options.SignIn.RequireConfirmedAccount)
                {
                    return RedirectToPage("RegisterConfirmation", new { email = Input.Email });
                }
                else
                {
                    await _signInManager.SignInAsync(user, isPersistent: false);
                    return LocalRedirect(returnUrl);
                }
            }
            foreach (var error in result.Errors)
            {
                ModelState.AddModelError(string.Empty, error.Description);
            }
        }

         //If we got this far, something failed, redisplay form
        return Page();
    }

The error is "Invalid expression term '=' " and it points to the line of return ??=Url.Content("~/Account/feeds"); How can I solve this error knowing that this class is a scaffolded item ??

Thanks.

Answer 1

??= is the Null Coalescing Operator . That one is syntax sugar. It was added with C# 7.3 and improoved with 8.0.

Note that the C# Version is entirely a compiler thing. It has nothing to do with the Target Framework. However the Backend Framework does mater, in the sense the the real commandline compilers VS is remoting might not yet support a new Dialect of C#:

https://www.c-sharpcorner.com/article/which-version-of-c-sharp-am-i-using-in-visual-studio-2019/

Answer 2

The Null Coalescing Assignment operator ( ??= ) is a feature introduced in C# 8. It appears that your project may not be correctly targeting this version of the language, or perhaps be unable to target it.

You can get what's essentially equivalent functionality to what this operator does fairly easily, though it's a bit more verbose.

returnUrl = returnUrl ?? Url.Content("~/Account/feeds");

You could also just check if the value is null, and then assign to it.

if(returnUrl == null)
    returnUrl = Url.Content("~/Account/feeds");

Answer 3

Severity Code Description Project File Line Suppression State Error (active) CS1525 Invalid expression term '=' EmployeeMngmnt C:\\Users\\LAP3\\source\\repos\\EmployeeMngmnt\\Views\\Home\\Details.cshtml

I have same error , I am using vs2019. please help me. this is my code

@{
    Layout = "~/Views/Shared/_layout.cshtml";
}

what is wrong with this code?## Heading ##