|To optimize performance and ensure that your application is interacting with the Betfair API as efficiently as possible, we strongly recommend the following as best practice.|
Expect: 100- Continue Header
Sending this header will result in the error: "The remote server returned an error: (417) Expectation Failed."
You should be aware that if using the .Net Framework you will need to set the relevant property in the ServicePointManager which then prevents the "Expect" header from being added:
System.Net.ServicePointManager.Expect100Continue = false;
Enabling HTTP compression