The request message was already sent. Cannot send the same request message multiple times.

[adamcti]

Hi I have the following code producing an error "The request message was already sent. Cannot send the same request message multiple times."

what is the fix because I assumed the code would work out of box...
`

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Net.Http;
using System.Threading.Tasks;
using Medidata.MAuth.Core;
namespace Medidata
{
public class RequestExample
{

    static async Task Main(string[] args)
    {

       
        var mauthSigningHander = new MAuthSigningHandler(
            new MAuthSigningOptions()
            {
                ApplicationUuid = new Guid("670e052b-6858-4a34-9b18-4cb44ddfec86"),
                PrivateKey = "C:/some/location/on/drive/key.pem"
            }
          );
        var client = new HttpClient(mauthSigningHander);
        
        var request = new HttpRequestMessage(HttpMethod.Get, "https://www.imedidata.com/api/v2/study_groups.json");

        request.Headers.Add("Accept", "application/json");
        request.Headers.Add("Mcc-Version", "v2019-04-12");

        var response = await client.SendAsync(request);
        
        response = await client.SendAsync(request);

        response.EnsureSuccessStatusCode();

        Console.WriteLine("The Response body is the following:");
        Console.WriteLine($"{await response.Content.ReadAsStringAsync()}");

        Console.WriteLine("\nPress ANY key to exit");
        Console.ReadKey();
    }
}

}

`

[zczhi]

Hi, As you know, the error message mentions that the same parameter is used twice as the request parameter. This position is wrong in your sample code.

        ...
        var response = await client.SendAsync(request);
        
        response = await client.SendAsync(request);
        ...

[GoncharovMain]

Attention! Not safe! To demonstrate internal implementation:

public static class HttpRequestMessageExtension
{
    public static void Reset(this HttpRequestMessage message)
    {
        Type type = message.GetType();

        /// From source code: https://github.com/microsoft/referencesource/blob/master/System/net/System/Net/Http/HttpRequestMessage.cs
        /// 
        /// private const int messageAlreadySent = 1; // signals that this message was already sent. 
        /// private const int messageNotYetSent = 0;
        // If this field is 0 (default), then the message wasn't sent by an HttpClient instance yet. If the field
        // value is 'messageSent', then the message was already sent and should not be sent again.
        /// private int sendStatus;
        
        /// But reflection find only _sendStatus field
        FieldInfo fieldStatusSend = type.GetField("_sendStatus", BindingFlags.NonPublic | BindingFlags.Instance);

        const int messageNotYetSent = 0;

        fieldStatusSend.SetValue(message, messageNotYetSent);
        /// Not disposing!
        // message.Dispose();
    }
}

static async Task Main(string[] args)
{
    ...
    var response = await client.SendAsync(request);
    request.Reset();
    response = await client.SendAsync(request);
    ...
}

Better use, for example, a property with expression-bodied property:

public class Entry
{
    private HttpMethod _method = HttpMethod.Get;
    private Uri _uri = new("https://www.imedidata.com/api/v2/study_groups.json");
    public HttpRequestMessage Request => new(_method , _uri)
    {
        Headers =
        {
            { "Accept", "application/json" },
            { "Mcc-Version", "v2019-04-12" },
        }
    }
}

static async Task Main(string[] args)
{
    ...
    Entry entry = new();
    var response = await client.SendAsync(entry.Request);
    response = await client.SendAsync(entry.Request);
    ...
}