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ParameterizedThreadStart Delegate

Definition

Represents the method that executes on a Thread.

public delegate void ParameterizedThreadStart(object? obj);
[System.Runtime.InteropServices.ComVisible(false)]
public delegate void ParameterizedThreadStart(object obj);
public delegate void ParameterizedThreadStart(object obj);

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 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.'

Remarks

When a managed thread is created, the method that executes on the thread is represented by:

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:

Extension Methods

GetMethodInfo(Delegate)

Gets an object that represents the method represented by the specified delegate.

Applies to

Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1

See also