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DispatcherPriority Enumeration

 

Describes the priorities at which operations can be invoked by way of the Dispatcher.

Namespace:   System.Windows.Threading
Assembly:  WindowsBase (in WindowsBase.dll)

public enum DispatcherPriority

Member nameDescription
ApplicationIdle

The enumeration value is 2. Operations are processed when the application is idle.

Background

The enumeration value is 4. Operations are processed after all other non-idle operations are completed.

ContextIdle

The enumeration value is 3. Operations are processed after background operations have completed.

DataBind

The enumeration value is 8. Operations are processed at the same priority as data binding.

Inactive

The enumeration value is 0. Operations are not processed.

Input

The enumeration value is 5. Operations are processed at the same priority as input.

Invalid

The enumeration value is -1. This is an invalid priority.

Loaded

The enumeration value is 6. Operations are processed when layout and render has finished but just before items at input priority are serviced. Specifically this is used when raising the Loaded event.

Normal

The enumeration value is 9. Operations are processed at normal priority. This is the typical application priority.

Render

The enumeration value is 7. Operations processed at the same priority as rendering.

Send

The enumeration value is 10. Operations are processed before other asynchronous operations. This is the highest priority.

SystemIdle

The enumeration value is 1. Operations are processed when the system is idle.

There is no specific system state or "idleness" corresponding to ApplicationIdle and ContextIdle in the current version of WPF. Both are still valid priorities; therefore, an operation with a priority of ContextIdle has a higher priority than an operation with a priority of SystemIdle.

The Dispatcher does not throttle the execution of an operation if it exceeds a certain percentage of the CPU. One way to throttle a process it to use a timer.

If an operation is posted using Invoke on its own Dispatcher at a priority of Send, the operation bypasses the queue and is immediately executed.

The following example is a call to BeginInvoke that passes a delegate which accepts an argument. The priority is set to Normal.

// Schedule the update function in the UI thread.
tomorrowsWeather.Dispatcher.BeginInvoke(
    System.Windows.Threading.DispatcherPriority.Normal,
    new OneArgDelegate(UpdateUserInterface), 
    weather);

.NET Framework
Available since 3.0
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