如何在ASP.NET核心Web API中发送带有错误http响应的正文？

// 自定义错误模型
public class ErrorResponseModel
{
    public int ErrorCode { get; set; }
    public string ErrorMessage { get; set; }
}

// 自定义错误处理中间件
public class ErrorHandlingMiddleware
{
    private readonly RequestDelegate _next;

    public ErrorHandlingMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            await HandleExceptionAsync(context, ex);
        }
    }

    private static Task HandleExceptionAsync(HttpContext context, Exception exception)
    {
        var statusCode = HttpStatusCode.InternalServerError; // 默认错误状态码
        var errorCode = 500; // 默认错误代码
        var errorMessage = "An error occurred."; // 默认错误消息

        // 根据异常类型设置合适的状态码和错误信息
        if (exception is BadRequestException)
        {
            statusCode = HttpStatusCode.BadRequest;
            errorCode = 400;
            errorMessage = "Bad request.";
        }
        else if (exception is NotFoundException)
        {
            statusCode = HttpStatusCode.NotFound;
            errorCode = 404;
            errorMessage = "Resource not found.";
        }

        // 构建错误响应模型
        var errorResponse = new ErrorResponseModel
        {
            ErrorCode = errorCode,
            ErrorMessage = errorMessage
        };

        // 设置响应内容和状态码
        context.Response.ContentType = "application/json";
        context.Response.StatusCode = (int)statusCode;

        // 将错误响应模型序列化为JSON并写入响应正文
        var json = JsonConvert.SerializeObject(errorResponse);
        return context.Response.WriteAsync(json);
    }
}

// 注册自定义错误处理中间件
public void Configure(IApplicationBuilder app)
{
    // ...

    app.UseMiddleware<ErrorHandlingMiddleware>();

    // ...
}

// 控制器中抛出异常
[HttpGet("{id}")]
public IActionResult Get(int id)
{
    var item = _repository.GetItem(id);
    if (item == null)
    {
        throw new NotFoundException();
    }

    return Ok(item);
}