.NET Core Web Api 配置ip访问

要配置.NET Core Web API允许特定IP地址访问，可以在应用程序启动时添加中间件。以下是一个示例中间件，它将允许特定IP地址的访问。

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using System.Net;
using System.Threading.Tasks;

public class IpRestrictionMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<IpRestrictionMiddleware> _logger;
    private readonly string[] _allowedIpAddresses;

    public IpRestrictionMiddleware(RequestDelegate next, ILogger<IpRestrictionMiddleware> logger, string[] allowedIpAddresses)
    {
        _next = next;
        _logger = logger;
        _allowedIpAddresses = allowedIpAddresses;
    }

    public async Task Invoke(HttpContext context)
    {
        var remoteIpAddress = context.Connection.RemoteIpAddress;

        if (_allowedIpAddresses.Contains(remoteIpAddress.ToString()))
        {
            await _next.Invoke(context);
        }
        else
        {
            _logger.LogWarning($"Request from {remoteIpAddress} rejected.");
            context.Response.StatusCode = (int)HttpStatusCode.Forbidden;
            await context.Response.WriteAsync("You are not authorized to access this resource.");
        }
    }
}

public static class IpRestrictionMiddlewareExtensions
{
    public static IApplicationBuilder UseIpRestriction(this IApplicationBuilder builder, string[] allowedIpAddresses)
    {
        return builder.UseMiddleware<IpRestrictionMiddleware>(allowedIpAddresses);
    }
}

在`Startup.cs`文件中，可以使用以下代码将中间件添加到管道中：

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // ...

    app.UseIpRestriction(new[] { "127.0.0.1", "::1" }); // add IP addresses to allow

    // ...
}

在上面的示例中，`IpRestrictionMiddleware`类将检查传入请求的远程IP地址，并与允许的IP地址列表进行比较。如果IP地址存在于列表中，则请求将被转发到下一个中间件。否则，请求将被拒绝，并返回HTTP状态码403（Forbidden）和错误消息。