ParameterizedThreadStart Delegate
Definition
Important
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Represents the method that executes on a Thread.
public delegate void ParameterizedThreadStart(System::Object ^ obj);
public delegate void ParameterizedThreadStart(object? obj);
[System.Runtime.InteropServices.ComVisible(false)]
public delegate void ParameterizedThreadStart(object obj);
public delegate void ParameterizedThreadStart(object obj);
type ParameterizedThreadStart = delegate of obj -> unit
[<System.Runtime.InteropServices.ComVisible(false)>]
type ParameterizedThreadStart = delegate of obj -> unit
Public Delegate Sub ParameterizedThreadStart(obj As Object)
Parameters
- obj
- Object
An object that contains data for the thread procedure.
- Attributes
Examples
The following code example uses a ParameterizedThreadStart delegate to execute a static method and an instance method. The first ParameterizedThreadStart delegate is represented by the static DoWork
method and the second is represented by the instance DoMoreWork
method. Both methods match the ParameterizedThreadStart delegate signature; that is, they have a single parameter of type Object and don't return a value.
Note
The Visual Basic and C# compilers infer the ParameterizedThreadStart delegate from the signatures of the DoWork
and DoMoreWork
methods, and call the correct constructor. Thus, there is no explicit constructor call in the code.
using namespace System;
using namespace System::Threading;
namespace SystemThreadingExample
{
public ref class Work
{
public:
void StartThreads()
{
// Start a thread that calls a parameterized static method.
Thread^ newThread = gcnew
Thread(gcnew ParameterizedThreadStart(Work::DoWork));
newThread->Start(42);
// Start a thread that calls a parameterized instance method.
Work^ someWork = gcnew Work;
newThread = gcnew Thread(
gcnew ParameterizedThreadStart(someWork,
&Work::DoMoreWork));
newThread->Start("The answer.");
}
static void DoWork(Object^ data)
{
Console::WriteLine("Static thread procedure. Data='{0}'",
data);
}
void DoMoreWork(Object^ data)
{
Console::WriteLine("Instance thread procedure. Data='{0}'",
data);
}
};
}
//Entry point of example application
int main()
{
SystemThreadingExample::Work^ samplework =
gcnew SystemThreadingExample::Work();
samplework->StartThreads();
}
// This example displays output like the following:
// Static thread procedure. Data='42'
// Instance thread procedure. Data='The answer.'
using System;
using System.Threading;
public class Work
{
public static void Main()
{
// Start a thread that calls a parameterized static method.
Thread newThread = new Thread(Work.DoWork);
newThread.Start(42);
// Start a thread that calls a parameterized instance method.
Work w = new Work();
newThread = new Thread(w.DoMoreWork);
newThread.Start("The answer.");
}
public static void DoWork(object data)
{
Console.WriteLine("Static thread procedure. Data='{0}'",
data);
}
public void DoMoreWork(object data)
{
Console.WriteLine("Instance thread procedure. Data='{0}'",
data);
}
}
// This example displays output like the following:
// Static thread procedure. Data='42'
// Instance thread procedure. Data='The answer.'
Imports System.Threading
Public Class Work
Shared Sub Main()
' Start a thread that calls a parameterized static method.
Dim newThread As New Thread(AddressOf Work.DoWork)
newThread.Start(42)
' Start a thread that calls a parameterized instance method.
Dim w As New Work()
newThread = New Thread(AddressOf w.DoMoreWork)
newThread.Start("The answer.")
End Sub
Public Shared Sub DoWork(ByVal data As Object)
Console.WriteLine("Static thread procedure. Data='{0}'",
data)
End Sub
Public Sub DoMoreWork(ByVal data As Object)
Console.WriteLine("Instance thread procedure. Data='{0}'",
data)
End Sub
End Class
' This example displays output like the following:
' Static thread procedure. Data='42'
' Instance thread procedure. Data='The answer.'
Remarks
When a managed thread is created, the method that executes on the thread is represented by:
A ThreadStart delegate that is passed to the Thread.Thread(ThreadStart) constructor. Any method that has no parameters and that returns
void
in C# or is aSub
procedure in Visual Basic can represent the delegate.A ParameterizedThreadStart delegate that is passed to the Thread.Thread(ParameterizedThreadStart) constructor. Any method that has a single parameter of type Object and that returns void in C# or is a Sub procedure in Visual Basic can represent the delegate.
The thread does not begin executing until the Thread.Start method is called. The ThreadStart or ParameterizedThreadStart delegate is invoked on the thread, and execution begins at the first line of the method represented by the delegate. In the case of the ParameterizedThreadStart delegate, the object that is passed to the Start(Object) method is passed to the delegate.
Note
Visual Basic and C# users can omit the ThreadStart or ParameterizedThreadStart delegate constructor when creating a thread. In Visual Basic, use the AddressOf
operator when passing your method to the Thread constructor; for example, Dim t As New Thread(AddressOf ThreadProc)
. In C#, simply specify the name of the thread procedure. The compiler selects the correct delegate constructor.
Note
When you create a ParameterizedThreadStart delegate for an instance method in C++, the first parameter of the constructor is the instance variable. For a static method, the first parameter of the constructor is zero. For a static method, the delegate constructor requires only one parameter: the address of the callback method, qualified by the class name.
The ParameterizedThreadStart delegate and the Thread.Start(Object) method overload make it easy to pass data to a thread procedure, but this technique is not type safe because any object can be passed to Thread.Start(Object). A more robust way to pass data to a thread procedure is to put both the thread procedure and the data fields into a worker object. For more information, see Creating Threads and Passing Data at Start Time.
The ParameterizedThreadStart delegate supports only a single parameter. You can pass multiple data items to the ParameterizedThreadStart by making that parameter one of the following:
An array.
A collection type, if all of the data items are of the same type.
A tuple type, such as Tuple<T1,T2> or Tuple<T1,T2,T3,T4>.
Extension Methods
GetMethodInfo(Delegate) |
Gets an object that represents the method represented by the specified delegate. |
Applies to
See also
.NET