Visual Basic 2015 Unleashed

The Old-Fashioned Way: The Asynchronous Programming Model

The Asynchronous Programming Model (APM) is still based on threading. In this model, an operation is launched on a separated thread via a method whose name starts with Begin (e.g., BeginWrite). A method like this must accept, among its parameters, an argument of type IAsyncResult. This is a special type used to store the result and the state of an asynchronous operation. The most important members of this interface are two properties: AsyncState (of type Object), which represents the result of the operation under the form of either a primitive or a composite type, and IsCompleted (of type Boolean), which returns if the operation actually completed. As another parameter, these methods ...