Question

Explain the use of ISynchronizeInvoke in cross thread invocation in .NET?

Answer 1

It’s just an interface which contains appropriate methods to:

• Check whether special handling is required (InvokeRequired)
• Invoke a delegate safely from a different thread, blocking until the action is completed (Invoke)
• Invoke a delegate safely from a different thread, returning immediately without blocking (BeginInvoke which can be coupled with EndInvoke to retrieve the result later)

The most commonly known implementation is Control in Windows Forms.

Basically the problem is that it’s not safe to access UI elements within arbitrary threads. These mechanisms allow calls to be marshalled between threads relatively easily. By only tying yourself to ISynchronizeInvoke instead of Control, you can avoid business classes from being tightly coupled to the UI.

EDIT: Stephen’s comment from below is worth repeating here:

It’s important to note that
ISynchronizeInvoke is outdated. The
SynchronizationContext abstraction is
more universal. Control is not just
the most commonly known
implementation; it’s the only
Microsoft one.