Edi.Captcha.AspNetCore

The Captcha module used in my blog

Usage

0. Install from NuGet

NuGet Package Manager

Install-Package Edi.Captcha

or .NET CLI

dotnet add package Edi.Captcha

1. Register in DI

services.AddSession(options =>
{
    options.IdleTimeout = TimeSpan.FromMinutes(20);
    options.Cookie.HttpOnly = true;
});

services.AddSessionBasedCaptcha();

// Don't forget to add this line in your `Configure` method.
 app.UseSession();

or you can customize the options

services.AddSessionBasedCaptcha(option =>
{
    option.Letters = "2346789ABCDEFGHJKLMNPRTUVWXYZ";
    option.SessionName = "CaptchaCode";
    option.CodeLength = 4;
});

2. Use DI in Controller

private readonly ISessionBasedCaptcha _captcha;

public SomeController(ISessionBasedCaptcha captcha)
{
    _captcha = captcha;
}

3. Add an Action to return captcha image

[Route("get-captcha-image")]
public IActionResult GetCaptchaImage()
{
    var s = _captcha.GenerateCaptchaImageFileStream(
        100,
        36,
        HttpContext.Session);
    return s;
}

4. Add CaptchaCode Property to Model

[Required]
[StringLength(4)]
public string CaptchaCode { get; set; }

5. View

<div class="col">
    <div class="input-group">
        <div class="input-group-prepend">
            <img id="img-captcha" src="~/get-captcha-image" />
        </div>
        <input type="text" 
               asp-for="CommentPostModel.CaptchaCode" 
               class="form-control" 
               placeholder="Captcha Code" 
               autocomplete="off" 
               minlength="4"
               maxlength="4" />
    </div>
    <span asp-validation-for="CommentPostModel.CaptchaCode" class="text-danger"></span>
</div>

6. Validate Input

_captcha.ValidateCaptchaCode(model.CommentPostModel.CaptchaCode, HttpContext.Session)

Refer to https://edi.wang/post/2018/10/13/generate-captcha-code-aspnet-core