Web API請求內容為空

Question

我有一個DelegatingHandler實現來記錄請求/響應內容：

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);
    }
}

但由於某種原因， requestContent即將出現。 request.Content.Length確認有內容，它只是沒有被提取。

有任何想法嗎？

Answer 1

讀取請求主體流並將其綁定到參數中，並且作為綁定的結果，流已經定位到最后。 這就是它變得空洞的原因。 如果你在request.Content.ReadAsStringAsync()之前尋找開頭，它應該工作。 而不是那樣，你可以在綁定發生之前先簡單地讀取請求體，有些事情是這樣的。

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);
    }
}