Thread Constructor (ParameterizedThreadStart)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Initializes a new instance of the Thread class, specifying a delegate that allows an object to be passed to the thread when the thread is started.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- start
- Type: System.Threading.ParameterizedThreadStart
A delegate that represents the methods to be invoked when this thread begins executing.
| Exception | Condition |
|---|---|
| ArgumentNullException | start is Nothing. |
A thread does not begin executing when it is created. To schedule the thread for execution, call the Start method. To pass a data object to the thread, use the Start(Object) method overload.
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Visual Basic and C# users can omit the ThreadStart or ParameterizedThreadStart constructor when creating a thread. The compilers automatically call the appropriate constructor. For Visual Basic, use the AddressOf operator when passing your method; for example, Dim t As New Thread(AddressOf ThreadProc). |
The following example shows how to create and start a thread by using a ParameterizedThreadStart delegate with a static method.
The example displays its output in a TextBlock on the user interface (UI) thread. To access the TextBlock from the callback thread, the example uses the Dispatcher property to obtain a Dispatcher object for the TextBlock, and then uses the Dispatcher.BeginInvoke method to make the cross-thread call.
For more information about thread creation, see Creating Threads and Passing Data at Start Time. For example code that uses this constructor and passes thread synchronization objects to thread procedures, see EventWaitHandle.
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To run this example, see Building examples that have static TextBlock controls for Windows Phone 8. |
Imports System.Threading Public Class Example Private Shared outputBlock As System.Windows.Controls.TextBlock Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) Example.outputBlock = outputBlock ' To start a thread using a static thread procedure, use the ' class name and method name when you create the ' ParameterizedThreadStart delegate. Visual Basic expands the ' AddressOf expression to the appropriate delegate creation ' syntax: ' New ParameterizedThreadStart(AddressOf Example.DoWork) ' Dim newThread As New Thread(AddressOf Example.DoWork) newThread.Start(42) End Sub ' Simulate work. To communicate with objects on the UI thread, get the ' Dispatcher for one of the UI objects. Use the Dispatcher object's ' BeginInvoke method to queue a delegate that will run on the UI thread, ' and therefore can safely access UI elements like the TextBlock. Private Shared Sub DoWork(ByVal state As Object) Dim data As Integer = CInt(state) Dim display As New Action(Of String)(AddressOf DisplayOutput) outputBlock.Dispatcher.BeginInvoke(display, _ String.Format("Shared thread procedure. Data={0}" & vbLf, data)) End Sub ' The Dispatcher.BeginInvoke method runs this helper method on the ' UI thread, so it can safely access the TextBlock that is used to ' display the output. Private Shared Sub DisplayOutput(msg) outputBlock.Text &= msg End Sub End Class ' This code example produces the following output: ' 'Shared thread procedure. Data='42'
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