Dynamically changing HttpClient.Timeout in .NET

Question

I need to change a HttpClient.Timeout property after it made a request(s). When I try, I get an exception:

This instance has already started one or more requests. Properties can only be modified before sending the first request.

Is there any way to avoid this?

Answer 1

There isn't much you can do to change this. This is just default behavior in the HttpClient implementation.

The Timeout property must be set before the GetRequestStream or GetResponse method is called. From HttpClient.Timeout Remark Section

In order to change the timeout, it would be best to create a new instance of an HttpClient.

client = new HttpClient();
client.Timeout = 20; //set new timeout

Answer 2

Internally the Timeout property is used to set up a CancellationTokenSource which will abort the async operation when that timeout is reached. Since some overloads of the HttpClient methods accept CancellationTokens, we can create helper methods to have a custom timeouts for specific operations:

public async Task<string> GetStringAsync(string requestUri, TimeSpan timeout)
{
    using (var cts = new CancellationTokenSource(timeout))
    {
        HttpResponseMessage response = await _httpClient.GetAsync(requestUri, cts.Token)
        response.EnsureSuccessStatusCode();

        return await response.Content.ReadAsStringAsync();
    }
}