dotnet-httpclient

Calling external HTTP service using HttpClient from a Web API Action

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Aha, I needed to do the following (return a Task rather then void): // GET api/values public async Task<IEnumerable<string>> Get() { var result = await GetExternalResponse(); return new string[] { result, “value2” }; } private async Task<string> GetExternalResponse() { var client = new HttpClient(); HttpResponseMessage response = await client.GetAsync(_address); response.EnsureSuccessStatusCode(); var result = await response.Content.ReadAsStringAsync(); … Read more

How can I get System.Net.Http.HttpClient to not follow 302 redirects?

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One of the overloads of the HttpClient constructor takes a WebRequestHandler argument. The HttpClient class uses this WebRequestHandler for sending requests. The WebRequestHandler class provides a property called AllowAutoRedirect to configure the redirect behaviour. Setting this property to false instructs the HttpClient to not follow redirect responses. Here is a small code sample: WebRequestHandler webRequestHandler … Read more

DelegatingHandler for response in WebApi

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Yes. You can do that in the continuation task. I explain it here. For example, this code (from the blog above) traces request URI and adds a dummy header to response. public class DummyHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { // work on the request Trace.WriteLine(request.RequestUri.ToString()); var response = … Read more

How to send a file and form data with HttpClient in C#

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Here’s code I’m using to post form information and a csv file using (var httpClient = new HttpClient()) { var surveyBytes = ConvertToByteArray(surveyResponse); httpClient.DefaultRequestHeaders.Add(“X-API-TOKEN”, _apiToken); httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(“application/json”)); var byteArrayContent = new ByteArrayContent(surveyBytes); byteArrayContent.Headers.ContentType = MediaTypeHeaderValue.Parse(“text/csv”); var response = await httpClient.PostAsync(_importUrl, new MultipartFormDataContent { {new StringContent(surveyId), “\”surveyId\””}, {byteArrayContent, “\”file\””, “\”feedback.csv\””} }); return response; } This is … Read more

How to disable Chunked Transfer Encoding in ASP.Net C# using HttpClient

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It looks like you need to set the Content-Length header too, if you don’t it seems to use the MaxRequestContentBufferSize on HttpClientHandler to chunk the data when sending it. Try using a StringContent, ByteArrayContent or StreamContent (If the steam is seekable) as these will be able to calculate the length for you. var content = … Read more

HttpClient: The uri string is too long

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If, like me, you’re faced with some wonky 3rd party web service that will only accept form content, you can work around the problem like this: // Let’s assume you’ve got your key-value pairs organised into a nice Dictionary<string, string> called formData var encodedItems = formData.Select(i => WebUtility.UrlEncode(i.Key) + “=” + WebUtility.UrlEncode(i.Value)); var encodedContent = … Read more

Should I cache and reuse HttpClient created from HttpClientFactory?

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HttpClient is only IDisposable because its HttpMessageHandler is IDisposable. In reality, it’s the HttpMessageHandler which should be long-lived. HttpClientFactory works by keeping a long-lived HttpMessageHandler internally. Whenever you ask for a HttpClient, it uses the long-lived HttpMessageHander, and tells the HttpClient not to dispose it when the HttpClient is disposed. You can see that on … Read more

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