為了能夠通過配置文件（appsettings.json）或通過代碼進行背景圖片與模板進行配置、可自定義資源類型、自定義驗證規則，本節創建一些擴展類，用來實現這些功能。

上一節內容：NET 6 實現滑動驗證碼（三）、介面

擴展類都放在了Extensions文件夾下

• CaptchaBuilderExtensions.cs
• CaptchaServiceCollectionExtensions.cs
• ServiceCollectionExtensions.cs
• SlideCaptchaException.cs

CaptchaBuilderExtensions.cs

CaptchaBuilderExtensions.cs實現了自定義提供驗證碼背景圖片資源或模板資源、自定義實現資源類型、替換預設驗證規則、禁用預設凹槽模板

using SlideCaptcha;
using SlideCaptcha.Interface;
using SlideCaptcha.Resources.Provider;
using System.Linq;

namespace Microsoft.Extensions.DependencyInjection
{
    public static class CaptchaBuilderExtensions
    {
        /// <summary>
        /// 自定義提供驗證碼背景圖片資源或模板資源
        /// </summary>
        /// <typeparam name="TProvider">自定義實現</typeparam>
        /// <param name="builder"></param>
        /// <returns></returns>
        public static CaptchaBuilder AddResourceProvider<TProvider>(this CaptchaBuilder builder) where TProvider : class, IResourceProvider
        {
            builder.Services.AddSingleton<IResourceProvider, TProvider>();
            return builder;
        }
        /// <summary>
        /// 自定義實現資源類型
        /// </summary>
        /// <typeparam name="THandler">自定義實現</typeparam>
        /// <param name="builder"></param>
        /// <returns></returns>
        public static CaptchaBuilder AddResourceHandler<THandler>(this CaptchaBuilder builder) where THandler : class, IResourceHandler
        {
            builder.Services.AddSingleton<IResourceHandler, THandler>();
            return builder;
        }
        /// <summary>
        /// 替換預設的驗證規則
        /// </summary>
        /// <typeparam name="TValidator">自定義驗證規則</typeparam>
        /// <param name="builder"></param>
        /// <returns></returns>
        public static CaptchaBuilder ReplaceValidator<TValidator>(this CaptchaBuilder builder) where TValidator : class, IValidator
        {
            builder.Services.Replace<IValidator, TValidator>();
            return builder;
        }
        /// <summary>
        /// 禁用預設凹槽模板
        /// </summary>
        /// <param name="builder"></param>
        /// <returns></returns>
        public static CaptchaBuilder DisableDefaultTemplates(this CaptchaBuilder builder)
        {
            var serviceDescriptor = builder.Services.FirstOrDefault(e => e.ImplementationType == typeof(EmbeddedResourceProvider));
            if (serviceDescriptor != null)
            {
                builder.Services.Remove(serviceDescriptor);
            }

            return builder;
        }
    }
}

CaptchaServiceCollectionExtensions.cs

CaptchaServiceCollectionExtensions.cs為自動註入必要的介面

using Microsoft.Extensions.Configuration;
using SlideCaptcha;
using SlideCaptcha.Constant;
using SlideCaptcha.Generator;
using SlideCaptcha.Interface;
using SlideCaptcha.Resources;
using SlideCaptcha.Resources.Handler;
using SlideCaptcha.Resources.Provider;
using SlideCaptcha.Storage;
using SlideCaptcha.Validator;
using System;

namespace Microsoft.Extensions.DependencyInjection
{
    public static class CaptchaServiceCollectionExtensions
    {
        /// <summary>
        /// 依賴註入必要的介面。
        /// </summary>
        /// <param name="services"></param>
        /// <param name="configuration"></param>
        /// <param name="optionsAction"></param>
        /// <returns></returns>
        public static CaptchaBuilder AddSlideCaptcha(this IServiceCollection services, IConfiguration configuration, Action<CaptchaOptions> optionsAction = default)
        {
            services.Configure<CaptchaOptions>(configuration?.GetSection("SlideCaptcha"));
            //對所需驗證的參數進行檢查，如果參數不合法就拋一個異常出來
            if (optionsAction != null) services.PostConfigure(optionsAction);

            var builder = new CaptchaBuilder(services);
            services.AddSingleton<IResourceProvider, OptionsResourceProvider>();
            services.AddSingleton<IResourceProvider, EmbeddedResourceProvider>();
            services.AddSingleton<IResourceHandlerManager, CachedResourceHandlerManager>();
            services.AddSingleton<IResourceManager, DefaultResourceManager>();
            services.AddSingleton<ISliderCaptchaImageGenerator, SliderCaptchaImageGenerator>();
            services.AddSingleton<IResourceHandler, FileResourceHandler>();
            services.AddSingleton<IResourceHandler, EmbeddedResourceHandler>();
            services.AddScoped<ICaptcha, ImageCaptcha>();
            services.AddScoped<IStorage, DefaultStorage>();
            services.AddScoped<IValidator, SimpleValidator>();
            return builder;
        }
    }
}

ServiceCollectionExtensions.cs

ServiceCollectionExtensions.cs用於實現IServiceCollection的Replace方法

using System;
using System.Collections.Generic;
using System.Linq;


namespace Microsoft.Extensions.DependencyInjection
{
    public static class ServiceCollectionExtensions
    {
        public static IServiceCollection Replace<TService, TImplementation>(this IServiceCollection services)
               where TImplementation : TService
        {
            return services.Replace<TService>(typeof(TImplementation));
        }

        public static IServiceCollection Replace<TService>(this IServiceCollection services, Type implementationType)
        {
            return services.Replace(typeof(TService), implementationType);
        }

        public static IServiceCollection Replace(this IServiceCollection services, Type serviceType, Type implementationType)
        {
            if (services == null)
            {
                throw new ArgumentNullException(nameof(services));
            }

            if (serviceType == null)
            {
                throw new ArgumentNullException(nameof(serviceType));
            }

            if (implementationType == null)
            {
                throw new ArgumentNullException(nameof(implementationType));
            }

            if (!services.TryGetDescriptors(serviceType, out var descriptors))
            {
                throw new ArgumentException($"No services found for {serviceType.FullName}.", nameof(serviceType));
            }

            foreach (var descriptor in descriptors)
            {
                var index = services.IndexOf(descriptor);

                services.Insert(index, descriptor.WithImplementationType(implementationType));

                services.Remove(descriptor);
            }

            return services;
        }

        private static bool TryGetDescriptors(this IServiceCollection services, Type serviceType, out ICollection<ServiceDescriptor> descriptors)
        {
            return (descriptors = services.Where(service => service.ServiceType == serviceType).ToArray()).Any();
        }

        private static ServiceDescriptor WithImplementationType(this ServiceDescriptor descriptor, Type implementationType)
        {
            return new ServiceDescriptor(descriptor.ServiceType, implementationType, descriptor.Lifetime);
        }
    }
}

SlideCaptchaException.cs

SlideCaptchaException.cs 實現自定義異常信息。

using System;

namespace SlideCaptcha.Exceptions
{
    public class SlideCaptchaException : Exception
    {
        public SlideCaptchaException() : base()
        {
        }

        public SlideCaptchaException(string message) : base(message)
        {
        }

        public SlideCaptchaException(string message, Exception innerException) : base(message, innerException)
        {
        }
    }
}

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