When you call a web service method that doesn't return a value (a void method), you don't want to waste time waiting until the call returns. But by default, the calling thread blocks until the server responds.
In such cases, you can use the OneWay Boolean attribute of the SoapDocumentMethod in the System.Web.Services.Protocols assembly. This attribute frees the calling thread (the client thread) immediately, instead of causing it to wait for the server response.
Note that the attribute is valid only for void methods.
Here's the syntax:
public void OneWayMethod()