When this property is set to true, client requests that use the POST method expect to receive a 100-Continue response from the server to indicate that the client should send the data to be posted. This mechanism allows clients to avoid sending large amounts of data over the network when the server, based on the request headers, intends to reject the request.

For example, assume the ServicePoint.Expect100Continue property is false. When the request is sent to the server, it includes the data. If, after reading the request headers, the server requires authentication and sends a 401 response, the client must resend the data with proper authentication headers.

If the ServicePoint.Expect100Continue property is true, the request headers are sent to the server. If the server has not rejected the request, it sends a 100-Continue response signaling that the data can be transmitted. If, as in the preceding example, the server requires authentication, it sends the 401 response and the client has not unnecessarily transmitted the data.

Changing the value of this property does not affect existing connections. Only new connections created after the change are affected.

The Expect 100-Continue behavior is fully described in IETF RFC 2616 Section 10.1.1.

Namespace: System.Net
Assembly: System (in System.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0