session-image.md

Images captcha base session

0. Install the required nuget package

       Install-Package NCaptcha.AspNetCore.SessionImages

1. Register in DI

   public void ConfigureServices(IServiceCollection services)
   {
       services.AddSession();
       services.AddSessionBasedImageCaptcha();
   }

2. Configure the session

   public void Configure(IApplicationBuilder app)
   {
       app.UseSession();
   }

3. Add a API for getting captcha image

   public class LoginModel : PageModel
   {
       private readonly ICaptchaGenerator _captchaGenerator;
   
       public LoginModel(ICaptchaGenerator captchaGenerator)
       {
           _captchaGenerator = captchaGenerator;
       }
   
       public async Task<IActionResult> OnGetCaptchaAsync() => await _captchaGenerator.GetCaptchaFileResultAsync();
   }

4. Validate the captcha

   public class LoginModel : PageModel
   {
       private readonly ICaptchaValidator _captchaValidator;
   
       public LoginModel(ICaptchaValidator captchaValidator)
       {
           _captchaValidator = captchaValidator;
       }
   
       public async Task<IActionResult> OnPostAsync()
       {
           if (!await _captchaValidator.ValidateAsync(Input.Captcha))
           {
               ModelState.AddModelError(nameof(InputModel.Captcha), "Invalid captcha.");
               return Page();
           }
       }
   }