向LocalDevelopmentImpersonation中间件传递IConfiguration遇构造函数错误求助

错误原因 #

你的LocalDevelopmentImpersonation中间件实现了IMiddleware接口，ASP.NET Core会通过依赖注入（DI）容器实例化这类中间件，而非直接使用UseMiddleware传递的参数。当前代码存在两个核心问题：

1. 构造函数依赖RequestDelegate，但该类型并非DI容器默认注册的服务，无法被自动解析。
2. 扩展方法中通过Options.Create(configuration)传递的是IOptions<IConfiguration>类型，与构造函数所需的IConfiguration参数类型不匹配，导致DI无法找到匹配的构造函数。

解决方案 #

方案1：改用基于约定的中间件（推荐，实现更简洁） #

移除IMiddleware接口实现，改用ASP.NET Core约定式中间件模式：

修改后的中间件类

namespace LocalDevelopmentImpersonation
{
    public sealed class LocalDevelopmentImpersonation
    {
        private readonly RequestDelegate _next;
        private readonly SafeAccessTokenHandle _safeAccessTokenHandle;
        private readonly bool _isLocal;

        public LocalDevelopmentImpersonation(RequestDelegate next, IConfiguration configuration)
        {
            _safeAccessTokenHandle = LocalDevelopmentImpersonationSetup.GetSafeAccessTokenHandle(out var receivedSafeAccessTokenSuccessfully);
            _next = next;
            _isLocal = LocalDevelopmentImpersonationSetup.IsLocal(receivedSafeAccessTokenSuccessfully, configuration);
        }

        public async Task InvokeAsync(HttpContext context)
        {
            if (_isLocal)
            {
                await WindowsIdentity.RunImpersonated(_safeAccessTokenHandle, async () =>
                {
                    await _next(context);
                });
            }
            else
            {
                await _next(context);
            }
        }
    }
}

修改后的扩展方法

namespace LocalDevelopmentImpersonation.ExtensionMethods
{
    public static class LocalDevelopmentImpersonationExtensions
    {
        public static IApplicationBuilder UseLocalDevelopmentImpersonation(this IApplicationBuilder app)
        {
            return app.UseMiddleware<LocalDevelopmentImpersonation>();
        }

        public static IApplicationBuilder UseLocalDevelopmentImpersonation(this IApplicationBuilder app, IConfiguration configuration)
        {
            if (app == null)
                throw new ArgumentNullException(nameof(app));
            if (configuration == null)
                throw new ArgumentNullException(nameof(configuration));

            return app.UseMiddleware<LocalDevelopmentImpersonation>(configuration);
        }
    }
}

调用代码保持不变即可，约定式中间件会自动将UseMiddleware传递的参数注入构造函数。

方案2：保留IMiddleware接口 #

如果坚持使用IMiddleware，需调整构造函数并注册中间件到DI容器：

修改后的中间件类

namespace LocalDevelopmentImpersonation
{
    public sealed class LocalDevelopmentImpersonation : IMiddleware
    {
        private readonly SafeAccessTokenHandle _safeAccessTokenHandle;
        private readonly bool _isLocal;

        // IMiddleware的InvokeAsync会自动接收RequestDelegate，构造函数无需依赖它
        public LocalDevelopmentImpersonation(IConfiguration configuration)
        {
            _safeAccessTokenHandle = LocalDevelopmentImpersonationSetup.GetSafeAccessTokenHandle(out var receivedSafeAccessTokenSuccessfully);
            _isLocal = LocalDevelopmentImpersonationSetup.IsLocal(receivedSafeAccessTokenSuccessfully, configuration);
        }

        public async Task InvokeAsync(HttpContext context, RequestDelegate next)
        {
            if (_isLocal)
            {
                await WindowsIdentity.RunImpersonated(_safeAccessTokenHandle, async () =>
                {
                    await next(context);
                });
            }
            else
            {
                await next(context);
            }
        }
    }
}

注册中间件到DI容器

在Program.cs中添加：

builder.Services.AddTransient<LocalDevelopmentImpersonation>();

简化扩展方法

namespace LocalDevelopmentImpersonation.ExtensionMethods
{
    public static class LocalDevelopmentImpersonationExtensions
    {
        public static IApplicationBuilder UseLocalDevelopmentImpersonation(this IApplicationBuilder app)
        {
            return app.UseMiddleware<LocalDevelopmentImpersonation>();
        }
    }
}

修改调用代码

var app = builder.Build();
app.UseLocalDevelopmentImpersonation();

此时DI会自动注入IConfiguration（默认已注册），无需手动传递。

内容的提问来源于stack exchange，提问作者Aaron C