How to clone a HttpRequestMessage when the original request has Content?

Question

I'm trying to clone a request using the method outlined in this answer: https://stackoverflow.com/a/18014515/406322

However, I get an ObjectDisposedException, if the original request has content.

How can you reliably clone a HttpRequestMessage?

Solution 1

This should do the trick:

    public static async Task<HttpRequestMessage> CloneHttpRequestMessageAsync(HttpRequestMessage req)
    {
        HttpRequestMessage clone = new HttpRequestMessage(req.Method, req.RequestUri);

        // Copy the request's content (via a MemoryStream) into the cloned object
        var ms = new MemoryStream();
        if (req.Content != null)
        {
            await req.Content.CopyToAsync(ms).ConfigureAwait(false);
            ms.Position = 0;
            clone.Content = new StreamContent(ms);

            // Copy the content headers
            if (req.Content.Headers != null)
                foreach (var h in req.Content.Headers)
                    clone.Content.Headers.Add(h.Key, h.Value);
        }


        clone.Version = req.Version;

        foreach (KeyValuePair<string, object> prop in req.Properties)
            clone.Properties.Add(prop);

        foreach (KeyValuePair<string, IEnumerable<string>> header in req.Headers)
            clone.Headers.TryAddWithoutValidation(header.Key, header.Value);

        return clone;
    }

Solution 2

If you call LoadIntoBufferAsync on the content, you can guarantee that the content is buffered inside the HttpContent object. The only problem remaining is that reading the stream does not reset the position, so you need to ReadAsStreamAsync and set the stream Position = 0.

My example is very similar to the one Carlos showed...

 private async Task<HttpResponseMessage> CloneResponseAsync(HttpResponseMessage response)
        {
            var newResponse = new HttpResponseMessage(response.StatusCode);
            var ms = new MemoryStream();

            foreach (var v in response.Headers) newResponse.Headers.TryAddWithoutValidation(v.Key, v.Value);
            if (response.Content != null)
            {
                await response.Content.CopyToAsync(ms).ConfigureAwait(false);
                ms.Position = 0;
                newResponse.Content = new StreamContent(ms);

                foreach (var v in response.Content.Headers) newResponse.Content.Headers.TryAddWithoutValidation(v.Key, v.Value);

            }
            return newResponse;
        }

```

Solution 3

Carlos's answer with some linq shortcuts:

public static async Task<HttpRequestMessage> Clone(this HttpRequestMessage httpRequestMessage)
{
    HttpRequestMessage httpRequestMessageClone = new HttpRequestMessage(httpRequestMessage.Method, httpRequestMessage.RequestUri);

    if (httpRequestMessage.Content != null)
    {
        var ms = new MemoryStream();
        await httpRequestMessage.Content.CopyToAsync(ms);
        ms.Position = 0;
        httpRequestMessageClone.Content = new StreamContent(ms);

        httpRequestMessage.Content.Headers?.ToList().ForEach(header => httpRequestMessageClone.Content.Headers.Add(header.Key, header.Value));
    }

    httpRequestMessageClone.Version = httpRequestMessage.Version;

    httpRequestMessage.Properties.ToList().ForEach(props => httpRequestMessageClone.Properties.Add(props));
    httpRequestMessage.Headers.ToList().ForEach(header => httpRequestMessageClone.Headers.TryAddWithoutValidation(header.Key, header.Value));

    return httpRequestMessageClone;
}

Comments

[Mauricio Aviles]

I just used this snippet and so far it works fine. @Prahbu: could your mark it as right answer?

[NStuke]

Link is now dead, perhaps you can add the relevant snippet to your answer?

[Eleasar]

The file was moved it seems and the LoadIntoBufferAsync was removed by a newer commit: github.com/tavis-software/Tavis.HttpCache/commit/…

[petko]

One note: this answer regards HttpResponseMessage cloning. The question was about cloning the request, not the response. The approach is fairly similar.

[Ivan Kukushkin]

Use "using" key word to avoid the memory leaks: using var ms = new MemoryStream();

[Yos]

as of .net 5 req.Content.Headers is never null, so there's no point in checking for null-ness. I just run the loop without the condition. Also req.Properties is obsolete and req.Options should be used instead.

[sferencik]

so in .NET 5, it should change to something like foreach (KeyValuePair<string, object?> option in req.Options) clone.Options.Set(new HttpRequestOptionsKey<object?>(option.Key), option.Value);

[MatteoSp]

why not just clone.Content = req.Content?