Web API请求内容为空

Question

I have a DelegatingHandler implementation to log request/response content:

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);
    }
}

but for some reason requestContent is coming up empty. request.Content.Length is confirming that there is content, it's just not being extracted.

Any ideas?

Answer 1

The request body stream is read and bound into parameters and as a result of binding, the stream has been positioned to the end. That is why it is coming as empty. If you seek to the beginning before request.Content.ReadAsStringAsync() , it should work. Instead of that, you can simply read the request body first before binding happens, some thing like this.

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);
    }
}