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DispatcherPriority Enumeration

.NET Framework 4

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

Namespace: System.Windows.Threading
Assembly: WindowsBase (in WindowsBase.dll)
XMLNS for XAML: Not mapped to an xmlns.

Syntax

C++

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public enum DispatcherPriority

Members

	Member name	Description
	Invalid	The enumeration value is -1. This is an invalid priority.
	Inactive	The enumeration value is 0. Operations are not processed.
	SystemIdle	The enumeration value is 1. Operations are processed when the system is idle.
	ApplicationIdle	The enumeration value is 2. Operations are processed when the application is idle.
	ContextIdle	The enumeration value is 3. Operations are processed after background operations have completed.
	Background	The enumeration value is 4. Operations are processed after all other non-idle operations are completed.
	Input	The enumeration value is 5. Operations are processed at the same priority as input.
	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.
	Render	The enumeration value is 7. Operations processed at the same priority as rendering.
	DataBind	The enumeration value is 8. Operations are processed at the same priority as data binding.
	Normal	The enumeration value is 9. Operations are processed at normal priority. This is the typical application priority.
	Send	The enumeration value is 10. Operations are processed before other asynchronous operations. This is the highest priority.

Remarks

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.

Examples

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

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

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

System.Windows.Threading Namespace

Other Resources

Threading Model

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