The request failed with HTTP status 417: Expectation failed.

When using WebServices and calling some Web Methods, you may come across to this exception: 

"The request failed with HTTP status 417: Expectation failed."

Solution:


It is easy, here are two alternative ways:

1) We need to have this line of code before making any web requests.

1:	System.Net.ServicePointManager.Expect100Continue = false;

2) Add these lines to the application's configuration file (between <configuration> and </configuration>):

1: 2: 3: 4: 5:

<system.net> <settings> <servicePointManager expect100Continue="false" /> </settings> </system.net>

While this workaround is nice, I think a better long term solution is to upgrade/replace the proxy server to handle 100-continue calls.

So far in this short tip we've learned what is Expect 100, how it is caused and how to workaround this expectation.