Web API请求内容为空

Question

我有一个DelegatingHandler实现来记录请求/响应内容：

public class RequestAndResponseLoggerDelegatingHandler : DelegatingHandler
{
    public IDataAccess Data { get; set; }

    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var started = DateTime.UtcNow;
        var response = await base.SendAsync(request, cancellationToken);
        await Log(started, request, response);
        return response;
    }

    private async Task Log(DateTime start, HttpRequestMessage request, HttpResponseMessage response)
    {
        var finished = DateTime.UtcNow;
        var requestContent = await request.Content.ReadAsStringAsync();
        var responseContent = await response.Content.ReadAsStringAsync();
        var info = new ApiLogEntry(start, finished, requestContent, responseContent, request, response);
        Data.Log(info);
    }
}

但由于某种原因， requestContent即将出现。 request.Content.Length确认有内容，它只是没有被提取。

有任何想法吗？

Answer 1

读取请求主体流并将其绑定到参数中，并且作为绑定的结果，流已经定位到最后。 这就是它变得空洞的原因。 如果你在request.Content.ReadAsStringAsync()之前寻找开头，它应该工作。 而不是那样，你可以在绑定发生之前先简单地读取请求体，有些事情是这样的。

public class RequestAndResponseLoggerDelegatingHandler : DelegatingHandler
{
    public IDataAccess Data { get; set; }

    protected override async Task<HttpResponseMessage> SendAsync(
                            HttpRequestMessage request, 
                                 CancellationToken cancellationToken)
    {
        var started = DateTime.UtcNow;
        var requestContent = await request.Content.ReadAsStringAsync();

        var response = await base.SendAsync(request, cancellationToken);

        var responseContent = await response.Content.ReadAsStringAsync();
        await Log(started, request, response, requestContent, responseContent);
        return response;
    }

    private async Task Log(DateTime start, HttpRequestMessage request, 
                             HttpResponseMessage response, string requestContent, 
                                string responseContent)
    {
        var finished = DateTime.UtcNow;           
        var info = new ApiLogEntry(start, finished, requestContent, responseContent, 
                                        request, response);
        Data.Log(info);
    }
}