Thread Constructor (ThreadStart)
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Thread Constructor (ThreadStart)

Initializes a new instance of the Thread class.

Namespace:  System.Threading
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
<SecuritySafeCriticalAttribute> _
Public Sub New ( _
	start As ThreadStart _
)

Parameters

start
Type: System.Threading.ThreadStart
A delegate that represents the methods to be invoked when this thread begins executing.

ExceptionCondition
ArgumentNullException

The start parameter is Nothing.

A thread does not begin executing when it is created. To schedule the thread for execution, call the Start method.

NoteNote:

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).

This section contains two examples. The first example shows how to create a thread that executes a static method, and the second example shows how to create a thread that executes an instance method.

The examples display their output in a TextBlock on the user interface (UI) thread. To access the TextBlock from the callback thread, the examples use the Dispatcher property to obtain a Dispatcher object for the TextBlock, and then use 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.

Example 1

The following example shows how to create a thread that executes a static method.


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 ThreadStart
      ' delegate. Visual Basic expands the AddressOf expression 
      ' to the appropriate delegate creation syntax:
      '    New ThreadStart(AddressOf Example.DoWork)
      '
      Dim newThread As New Thread(AddressOf Example.DoWork)
      newThread.Start()

   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()
      Dim display As New Action(Of String)(AddressOf DisplayOutput)

      outputBlock.Dispatcher.BeginInvoke(display, _
         "Hello from a Shared thread procedure." & vbCrLf)
   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:
'
'Hello from a Shared thread procedure.


Example 2

The following example shows how to create a thread that executes an instance method.


Imports System.Threading

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' To start a thread using an instance method for the thread 
      ' procedure, use the instance variable and method name when 
      ' you create the ThreadStart delegate. Visual Basic expands 
      ' the AddressOf expression to the appropriate delegate 
      ' creation syntax:
      '    New ThreadStart(AddressOf w.DoMoreWork)
      '
      Dim w As New Work()
      w.Data = 42
      w.Output = outputBlock

      Dim newThread As Thread = New Thread(AddressOf w.DoMoreWork)
      newThread.Start()
   End Sub

End Class

Public Class Work
   Public Data As Integer
   Public Output As System.Windows.Controls.TextBlock

   ' 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.
   Public Sub DoMoreWork()
      Dim display As New Action(Of String)(AddressOf DisplayOutput)

      Output.Dispatcher.BeginInvoke(display, _
         String.Format("Instance thread procedure. Data={0}", Data) & vbCrLf)
   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 Sub DisplayOutput(msg)
      Output.Text &= msg
   End Sub

End Class

' This code example produces the following output:
'
'Instance thread procedure. Data=42


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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