ParameterizedThreadStart Delegate
Collapse the table of content
Expand the table of content

ParameterizedThreadStart Delegate


Represents the method that executes on a Thread.

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

public delegate void ParameterizedThreadStart(
	object obj


Type: System.Object

An object that contains data for the thread procedure.

When a managed thread is created, the method that executes on the thread is represented by a ThreadStart delegate or a ParameterizedThreadStart delegate that is passed to the Thread constructor. 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.


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.


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:

The following code example shows the syntax for creating and using a ParameterizedThreadStart delegate with a static method and an instance method.


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 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);

        // 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}'",

    public void DoMoreWork(object data)
        Console.WriteLine("Instance thread procedure. Data='{0}'",
// This example displays output like the following:
//       Static thread procedure. Data='42'
//       Instance thread procedure. Data='The answer.'

.NET Framework
Available since 2.0
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Return to top
© 2016 Microsoft