HTTP POST Returns Error: 417 “Expectation Failed.”

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When I try to POST to a URL it results in the following exception:

The remote server returned an error:
(417) Expectation Failed.

Here’s a sample code:

var client = new WebClient();

var postData = new NameValueCollection();
postData.Add("postParamName", "postParamValue");

byte[] responseBytes = client.UploadValues("http://...", postData);
string response = Encoding.UTF8.GetString(responseBytes); // (417) Expectation Failed.

Using an HttpWebRequest/HttpWebResponse pair or an HttpClient doesn’t make a difference.

What’s causing this exception?

10 Answers
10

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