Dispatcher.Invoke Method (DispatcherPriority, TimeSpan, Delegate, Object)
Executes the specified delegate at the specified priority with the specified argument synchronously on the thread the Dispatcher is associated with.
Assembly: WindowsBase (in WindowsBase.dll)
[<BrowsableAttribute(false)>] member Invoke : priority:DispatcherPriority * timeout:TimeSpan * method:Delegate * arg:Object -> Object
- Type: System.Windows.Threading.DispatcherPriority
The priority, relative to the other pending operations in the Dispatcher event queue, the specified method is invoked.
- Type: System.TimeSpan
The maximum time to wait for the operation to finish.
- Type: System.Delegate
A delegate to a method that takes multiple arguments, which is pushed onto the Dispatcher event queue.
- Type: System.Object
An object to pass as an argument to the given method. This can be a null reference (Nothing in Visual Basic) if no arguments are needed.
Return ValueType: System.Object
The return value from the delegate being invoked or a null reference (Nothing in Visual Basic) if the delegate has no return value.
Arg can be a null reference (Nothing in Visual Basic) if an argument is not needed
In WPF, only the thread that created a DispatcherObject may access that object. For example, a background thread that is spun off from the main UI thread cannot update the contents of a Button that was created on the UI thread. In order for the background thread to access the Content property of the Button, the background thread must delegate the work to the Dispatcher associated with the UI thread. This is accomplished by using either Invoke or BeginInvoke. Invoke is synchronous and BeginInvoke is asynchronous. The operation is added to the event queue of the Dispatcher at the specified DispatcherPriority.
Invoke is a synchronous operation; therefore, control will not return to the calling object until after the callback returns.