Dispatcher.Invoke Method

Definition

Executes the specified delegate synchronously on the thread the Dispatcher is associated with.

Overloads

Invoke(DispatcherPriority, TimeSpan, Delegate, Object, Object[])

Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

Invoke(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.

Invoke(DispatcherPriority, Delegate, Object, Object[])

Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

Invoke(Action, DispatcherPriority, CancellationToken, TimeSpan)

Executes the specified Action synchronously at the specified priority on the thread the Dispatcher is associated with.

Invoke(DispatcherPriority, TimeSpan, Delegate)

Executes the specified delegate synchronously at the specified priority and with the specified time-out value on the thread the Dispatcher was created.

Invoke(DispatcherPriority, Delegate, Object)

Executes the specified delegate at the specified priority with the specified argument synchronously on the thread the Dispatcher is associated with.

Invoke(Delegate, TimeSpan, DispatcherPriority, Object[])

Executes the specified delegate within the designated time span at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

Invoke(Delegate, TimeSpan, Object[])

Executes the specified delegate within the designated time span at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

Invoke(Action, DispatcherPriority, CancellationToken)

Executes the specified Action synchronously at the specified priority on the thread the Dispatcher is associated with.

Invoke(DispatcherPriority, Delegate)

Executes the specified delegate synchronously at the specified priority on the thread that the Dispatcher is associated with.

Invoke(Delegate, Object[])

Executes the specified delegate with the specified arguments synchronously on the thread the Dispatcher is associated with.

Invoke(Action, DispatcherPriority)

Executes the specified Action synchronously at the specified priority on the thread the Dispatcher is associated with.

Invoke(Action)

Executes the specified Action synchronously on the thread the Dispatcher is associated with.

Invoke(Delegate, DispatcherPriority, Object[])

Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

Invoke<TResult>(Func<TResult>)

Executes the specified Func<TResult> synchronously on the thread the Dispatcher is associated with.

Invoke<TResult>(Func<TResult>, DispatcherPriority)

Executes the specified Func<TResult> synchronously at the specified priority on the thread the Dispatcher is associated with.

Invoke<TResult>(Func<TResult>, DispatcherPriority, CancellationToken)

Executes the specified Func<TResult> synchronously at the specified priority on the thread the Dispatcher is associated with.

Invoke<TResult>(Func<TResult>, DispatcherPriority, CancellationToken, TimeSpan)

Executes the specified Func<TResult> synchronously at the specified priority on the thread the Dispatcher is associated with.

Examples

The following example places a delegate onto a Dispatcher at Normal using Invoke.

// Places the delegate onto the UI Thread's Dispatcher
private void timer_Elapsed(object sender, ElapsedEventArgs e)
{
    // Place delegate on the Dispatcher.
    this.Dispatcher.Invoke(DispatcherPriority.Normal,
        new TimerDispatcherDelegate(TimerWorkItem));
}
' Places the delegate onto the UI Thread's Dispatcher
Private Sub timer_Elapsed(ByVal sender As Object, ByVal e As ElapsedEventArgs)
    ' Place delegate on the Dispatcher.
    Me.Dispatcher.Invoke(DispatcherPriority.Normal, New TimerDispatcherDelegate(AddressOf TimerWorkItem))
End Sub

Remarks

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.

Invoke(DispatcherPriority, TimeSpan, Delegate, Object, Object[])

Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(System::Windows::Threading::DispatcherPriority priority, TimeSpan timeout, Delegate ^ method, System::Object ^ arg, ... cli::array <System::Object ^> ^ args);
[System.ComponentModel.Browsable(false)]
public object Invoke (System.Windows.Threading.DispatcherPriority priority, TimeSpan timeout, Delegate method, object arg, params object[] args);
[<System.ComponentModel.Browsable(false)>]
member this.Invoke : System.Windows.Threading.DispatcherPriority * TimeSpan * Delegate * obj * obj[] -> obj
Public Function Invoke (priority As DispatcherPriority, timeout As TimeSpan, method As Delegate, arg As Object, ParamArray args As Object()) As Object

Parameters

priority
DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, with which the specified method is invoked.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. Once the operation has started, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

method
Delegate

A delegate to a method that takes multiple arguments, which is pushed onto the Dispatcher event queue.

arg
Object

An object to pass as an argument to the specified method.

args
Object[]

An array of objects to pass as arguments to the specified method.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Attributes

Exceptions

priority is equal to Inactive.

method is null.

timeout is a negative number other than -1, and this method was invoked across threads.

Remarks

arg can be null 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.

Invoke(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.

public:
 System::Object ^ Invoke(System::Windows::Threading::DispatcherPriority priority, TimeSpan timeout, Delegate ^ method, System::Object ^ arg);
[System.ComponentModel.Browsable(false)]
public object Invoke (System.Windows.Threading.DispatcherPriority priority, TimeSpan timeout, Delegate method, object arg);
[<System.ComponentModel.Browsable(false)>]
member this.Invoke : System.Windows.Threading.DispatcherPriority * TimeSpan * Delegate * obj -> obj
Public Function Invoke (priority As DispatcherPriority, timeout As TimeSpan, method As Delegate, arg As Object) As Object

Parameters

priority
DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, with which the specified method is invoked.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. Once the operation has started, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

method
Delegate

A delegate to a method that takes multiple arguments, which is pushed onto the Dispatcher event queue.

arg
Object

An object to pass as an argument to the given method. This can be null if no arguments are needed.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Attributes

Exceptions

priority is equal to Inactive.

priority is not a valid priority.

method is null.

Remarks

arg can be null 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.

Invoke(DispatcherPriority, Delegate, Object, Object[])

Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(System::Windows::Threading::DispatcherPriority priority, Delegate ^ method, System::Object ^ arg, ... cli::array <System::Object ^> ^ args);
[System.ComponentModel.Browsable(false)]
public object Invoke (System.Windows.Threading.DispatcherPriority priority, Delegate method, object arg, params object[] args);
[<System.ComponentModel.Browsable(false)>]
member this.Invoke : System.Windows.Threading.DispatcherPriority * Delegate * obj * obj[] -> obj
Public Function Invoke (priority As DispatcherPriority, method As Delegate, arg As Object, ParamArray args As Object()) As Object

Parameters

priority
DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, with which the specified method is invoked.

method
Delegate

A delegate to a method that takes multiple arguments, which is pushed onto the Dispatcher event queue.

arg
Object

An object to pass as an argument to the given method.

args
Object[]

An array of objects to pass as arguments to the given method.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Attributes

Exceptions

priority is equal to Inactive.

priority is not a valid priority.

method is null.

Remarks

arg can be null 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.

Invoke(Action, DispatcherPriority, CancellationToken, TimeSpan)

Executes the specified Action synchronously at the specified priority on the thread the Dispatcher is associated with.

public:
 void Invoke(Action ^ callback, System::Windows::Threading::DispatcherPriority priority, System::Threading::CancellationToken cancellationToken, TimeSpan timeout);
public void Invoke (Action callback, System.Windows.Threading.DispatcherPriority priority, System.Threading.CancellationToken cancellationToken, TimeSpan timeout);
member this.Invoke : Action * System.Windows.Threading.DispatcherPriority * System.Threading.CancellationToken * TimeSpan -> unit
Public Sub Invoke (callback As Action, priority As DispatcherPriority, cancellationToken As CancellationToken, timeout As TimeSpan)

Parameters

callback
Action

An Action delegate to invoke through the dispatcher.

priority
DispatcherPriority

The priority that determines the order in which the specified callback is invoked relative to the other pending operations in the Dispatcher.

cancellationToken
CancellationToken

An object that indicates whether to cancel the action.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. Once the operation has started, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

Exceptions

callback is null.

timeout is a negative number other than -1, and this method was invoked across threads.

priority is not a valid priority.

Invoke(DispatcherPriority, TimeSpan, Delegate)

Executes the specified delegate synchronously at the specified priority and with the specified time-out value on the thread the Dispatcher was created.

public:
 System::Object ^ Invoke(System::Windows::Threading::DispatcherPriority priority, TimeSpan timeout, Delegate ^ method);
[System.ComponentModel.Browsable(false)]
public object Invoke (System.Windows.Threading.DispatcherPriority priority, TimeSpan timeout, Delegate method);
[<System.ComponentModel.Browsable(false)>]
member this.Invoke : System.Windows.Threading.DispatcherPriority * TimeSpan * Delegate -> obj
Public Function Invoke (priority As DispatcherPriority, timeout As TimeSpan, method As Delegate) As Object

Parameters

priority
DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, with which the specified method is invoked.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. Once the operation has started, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

method
Delegate

The delegate to a method that takes no arguments, which is pushed onto the Dispatcher event queue.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Attributes

Exceptions

method is null.

timeout is a negative number other than -1, and this method was invoked across threads.

priority is equal to Inactive.

priority is not a valid priority.

Remarks

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.

Invoke(DispatcherPriority, Delegate, Object)

Executes the specified delegate at the specified priority with the specified argument synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(System::Windows::Threading::DispatcherPriority priority, Delegate ^ method, System::Object ^ arg);
[System.ComponentModel.Browsable(false)]
public object Invoke (System.Windows.Threading.DispatcherPriority priority, Delegate method, object arg);
[<System.ComponentModel.Browsable(false)>]
member this.Invoke : System.Windows.Threading.DispatcherPriority * Delegate * obj -> obj
Public Function Invoke (priority As DispatcherPriority, method As Delegate, arg As Object) As Object

Parameters

priority
DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, with which the specified method is invoked.

method
Delegate

A delegate to a method that takes one argument, which is pushed onto the Dispatcher event queue.

arg
Object

An object to pass as an argument to the given method.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Attributes

Exceptions

priority is equal to Inactive.

priority is not a valid priority.

method is null.

Remarks

arg can be null 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.

Invoke(Delegate, TimeSpan, DispatcherPriority, Object[])

Executes the specified delegate within the designated time span at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(Delegate ^ method, TimeSpan timeout, System::Windows::Threading::DispatcherPriority priority, ... cli::array <System::Object ^> ^ args);
public object Invoke (Delegate method, TimeSpan timeout, System.Windows.Threading.DispatcherPriority priority, params object[] args);
member this.Invoke : Delegate * TimeSpan * System.Windows.Threading.DispatcherPriority * obj[] -> obj
Public Function Invoke (method As Delegate, timeout As TimeSpan, priority As DispatcherPriority, ParamArray args As Object()) As Object

Parameters

method
Delegate

A delegate to a method that takes parameters specified in args, which is pushed onto the Dispatcher event queue.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. Once the operation has started, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

priority
DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, with which the specified method is invoked.

args
Object[]

An array of objects to pass as arguments to the given method. Can be null.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Exceptions

method is null.

timeout is a negative number other than -1, and this method was invoked across threads.

priority is equal to Inactive.

priority is not a valid priority.

Remarks

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.

Invoke(Delegate, TimeSpan, Object[])

Executes the specified delegate within the designated time span at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(Delegate ^ method, TimeSpan timeout, ... cli::array <System::Object ^> ^ args);
public object Invoke (Delegate method, TimeSpan timeout, params object[] args);
member this.Invoke : Delegate * TimeSpan * obj[] -> obj
Public Function Invoke (method As Delegate, timeout As TimeSpan, ParamArray args As Object()) As Object

Parameters

method
Delegate

A delegate to a method that takes parameters specified in args, which is pushed onto the Dispatcher event queue.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. However, once the operation starts, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

args
Object[]

An array of objects to pass as arguments to the given method. Can be null if no arguments are needed.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Exceptions

method is null.

timeout is a negative number other than -1, and you're invoking across threads.

Remarks

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 won't return to the calling object until after the callback returns.

Invoke(Action, DispatcherPriority, CancellationToken)

Executes the specified Action synchronously at the specified priority on the thread the Dispatcher is associated with.

public:
 void Invoke(Action ^ callback, System::Windows::Threading::DispatcherPriority priority, System::Threading::CancellationToken cancellationToken);
public void Invoke (Action callback, System.Windows.Threading.DispatcherPriority priority, System.Threading.CancellationToken cancellationToken);
member this.Invoke : Action * System.Windows.Threading.DispatcherPriority * System.Threading.CancellationToken -> unit
Public Sub Invoke (callback As Action, priority As DispatcherPriority, cancellationToken As CancellationToken)

Parameters

callback
Action

A delegate to invoke through the dispatcher.

priority
DispatcherPriority

The priority that determines the order in which the specified callback is invoked relative to the other pending operations in the Dispatcher.

cancellationToken
CancellationToken

An object that indicates whether to cancel the action.

Invoke(DispatcherPriority, Delegate)

Executes the specified delegate synchronously at the specified priority on the thread that the Dispatcher is associated with.

public:
 System::Object ^ Invoke(System::Windows::Threading::DispatcherPriority priority, Delegate ^ method);
[System.ComponentModel.Browsable(false)]
public object Invoke (System.Windows.Threading.DispatcherPriority priority, Delegate method);
[<System.ComponentModel.Browsable(false)>]
member this.Invoke : System.Windows.Threading.DispatcherPriority * Delegate -> obj
Public Function Invoke (priority As DispatcherPriority, method As Delegate) As Object

Parameters

priority
DispatcherPriority

The priority with which the specified method is invoked, relative to the other pending operations in the Dispatcher event queue.

method
Delegate

A delegate to a method that takes no arguments, which is pushed onto the Dispatcher event queue.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Attributes

Exceptions

priority is equal to Inactive.

priority is not a valid priority.

method is null.

Examples

The following example places a delegate onto a Dispatcher at Normal using Invoke.

// Places the delegate onto the UI Thread's Dispatcher
private void timer_Elapsed(object sender, ElapsedEventArgs e)
{
    // Place delegate on the Dispatcher.
    this.Dispatcher.Invoke(DispatcherPriority.Normal,
        new TimerDispatcherDelegate(TimerWorkItem));
}
' Places the delegate onto the UI Thread's Dispatcher
Private Sub timer_Elapsed(ByVal sender As Object, ByVal e As ElapsedEventArgs)
    ' Place delegate on the Dispatcher.
    Me.Dispatcher.Invoke(DispatcherPriority.Normal, New TimerDispatcherDelegate(AddressOf TimerWorkItem))
End Sub

Remarks

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.

Invoke(Delegate, Object[])

Executes the specified delegate with the specified arguments synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(Delegate ^ method, ... cli::array <System::Object ^> ^ args);
public object Invoke (Delegate method, params object[] args);
member this.Invoke : Delegate * obj[] -> obj
Public Function Invoke (method As Delegate, ParamArray args As Object()) As Object

Parameters

method
Delegate

A delegate to a method that takes parameters specified in args, which is pushed onto the Dispatcher event queue.

args
Object[]

An array of objects to pass as arguments to the given method. Can be null.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Remarks

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.

Invoke(Action, DispatcherPriority)

Executes the specified Action synchronously at the specified priority on the thread the Dispatcher is associated with.

public:
 void Invoke(Action ^ callback, System::Windows::Threading::DispatcherPriority priority);
public void Invoke (Action callback, System.Windows.Threading.DispatcherPriority priority);
member this.Invoke : Action * System.Windows.Threading.DispatcherPriority -> unit
Public Sub Invoke (callback As Action, priority As DispatcherPriority)

Parameters

callback
Action

A delegate to invoke through the dispatcher.

priority
DispatcherPriority

The priority that determines the order in which the specified callback is invoked relative to the other pending operations in the Dispatcher.

Invoke(Action)

Executes the specified Action synchronously on the thread the Dispatcher is associated with.

public:
 void Invoke(Action ^ callback);
public void Invoke (Action callback);
member this.Invoke : Action -> unit
Public Sub Invoke (callback As Action)

Parameters

callback
Action

A delegate to invoke through the dispatcher.

Invoke(Delegate, DispatcherPriority, Object[])

Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

public:
 System::Object ^ Invoke(Delegate ^ method, System::Windows::Threading::DispatcherPriority priority, ... cli::array <System::Object ^> ^ args);
public object Invoke (Delegate method, System.Windows.Threading.DispatcherPriority priority, params object[] args);
member this.Invoke : Delegate * System.Windows.Threading.DispatcherPriority * obj[] -> obj
Public Function Invoke (method As Delegate, priority As DispatcherPriority, ParamArray args As Object()) As Object

Parameters

method
Delegate

A delegate to a method that takes parameters specified in args, which is pushed onto the Dispatcher event queue.

priority
DispatcherPriority

The priority with which the specified method is invoked, relative to the other pending operations in the Dispatcher event queue.

args
Object[]

An array of objects to pass as arguments to the given method. Can be null.

Returns

Object

The return value from the delegate being invoked or null if the delegate has no return value.

Remarks

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.

Invoke<TResult>(Func<TResult>)

Executes the specified Func<TResult> synchronously on the thread the Dispatcher is associated with.

public:
generic <typename TResult>
 TResult Invoke(Func<TResult> ^ callback);
public TResult Invoke<TResult> (Func<TResult> callback);
member this.Invoke : Func<'Result> -> 'Result
Public Function Invoke(Of TResult) (callback As Func(Of TResult)) As TResult

Type Parameters

TResult

The return value type of the specified delegate.

Parameters

callback
Func<TResult>

A delegate to invoke through the dispatcher.

Returns

TResult

The value returned by callback.

Invoke<TResult>(Func<TResult>, DispatcherPriority)

Executes the specified Func<TResult> synchronously at the specified priority on the thread the Dispatcher is associated with.

public:
generic <typename TResult>
 TResult Invoke(Func<TResult> ^ callback, System::Windows::Threading::DispatcherPriority priority);
public TResult Invoke<TResult> (Func<TResult> callback, System.Windows.Threading.DispatcherPriority priority);
member this.Invoke : Func<'Result> * System.Windows.Threading.DispatcherPriority -> 'Result
Public Function Invoke(Of TResult) (callback As Func(Of TResult), priority As DispatcherPriority) As TResult

Type Parameters

TResult

The return value type of the specified delegate.

Parameters

callback
Func<TResult>

A delegate to invoke through the dispatcher.

priority
DispatcherPriority

The priority that determines the order in which the specified callback is invoked relative to the other pending operations in the Dispatcher.

Returns

TResult

The value returned by callback.

Invoke<TResult>(Func<TResult>, DispatcherPriority, CancellationToken)

Executes the specified Func<TResult> synchronously at the specified priority on the thread the Dispatcher is associated with.

public:
generic <typename TResult>
 TResult Invoke(Func<TResult> ^ callback, System::Windows::Threading::DispatcherPriority priority, System::Threading::CancellationToken cancellationToken);
public TResult Invoke<TResult> (Func<TResult> callback, System.Windows.Threading.DispatcherPriority priority, System.Threading.CancellationToken cancellationToken);
member this.Invoke : Func<'Result> * System.Windows.Threading.DispatcherPriority * System.Threading.CancellationToken -> 'Result
Public Function Invoke(Of TResult) (callback As Func(Of TResult), priority As DispatcherPriority, cancellationToken As CancellationToken) As TResult

Type Parameters

TResult

The return value type of the specified delegate.

Parameters

callback
Func<TResult>

A delegate to invoke through the dispatcher.

priority
DispatcherPriority

The priority that determines the order in which the specified callback is invoked relative to the other pending operations in the Dispatcher.

cancellationToken
CancellationToken

An object that indicates whether to cancel the operation.

Returns

TResult

The value returned by callback.

Invoke<TResult>(Func<TResult>, DispatcherPriority, CancellationToken, TimeSpan)

Executes the specified Func<TResult> synchronously at the specified priority on the thread the Dispatcher is associated with.

public:
generic <typename TResult>
 TResult Invoke(Func<TResult> ^ callback, System::Windows::Threading::DispatcherPriority priority, System::Threading::CancellationToken cancellationToken, TimeSpan timeout);
public TResult Invoke<TResult> (Func<TResult> callback, System.Windows.Threading.DispatcherPriority priority, System.Threading.CancellationToken cancellationToken, TimeSpan timeout);
member this.Invoke : Func<'Result> * System.Windows.Threading.DispatcherPriority * System.Threading.CancellationToken * TimeSpan -> 'Result
Public Function Invoke(Of TResult) (callback As Func(Of TResult), priority As DispatcherPriority, cancellationToken As CancellationToken, timeout As TimeSpan) As TResult

Type Parameters

TResult

The return value type of the specified delegate.

Parameters

callback
Func<TResult>

A delegate to invoke through the dispatcher.

priority
DispatcherPriority

The priority that determines the order in which the specified callback is invoked relative to the other pending operations in the Dispatcher.

cancellationToken
CancellationToken

An object that indicates whether to cancel the operation.

timeout
TimeSpan

The maximum amount of time to wait for the operation to start. Once the operation has started, it will complete before this method returns. To specify an infinite wait, use a value of -1. In a same-thread call, any other negative value is converted to -1, resulting in an infinite wait. In a cross-thread call, any other negative value throws an ArgumentOutOfRangeException.

Returns

TResult

The value returned by callback.

Exceptions

callback is null.

timeout is a negative number other than -1, and the method was invoked across threads.

priority is not a valid priority.

Applies to