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Process.Start Method (String)

Starts a process resource by specifying the name of a document or application file and associates the resource with a new Process component.

Namespace: System.Diagnostics
Assembly: System (in system.dll)

Public Shared Function Start ( _
	fileName As String _
) As Process
Dim fileName As String
Dim returnValue As Process

returnValue = Process.Start(fileName)
public static Process Start (
	String fileName
public static function Start (
	fileName : String
) : Process



The name of a document or application file to run in the process.

Return Value

A new Process component that is associated with the process resource, or a null reference (Nothing in Visual Basic), if no process resource is started (for example, if an existing process is reused).

Exception typeCondition


The fileName parameter is a null reference (Nothing in Visual Basic).


There was an error in opening the associated file.


The process object has already been disposed.


The PATH environment variable has a string containing quotes.

Use this overload to start a process resource by specifying its file name. The overload associates the resource with a new Process component. If the process is already running, no additional process resource is started. Instead, the existing process resource is reused and no new Process component is created. In such a case, instead of returning a new Process component, Start returns a null reference (Nothing in Visual Basic) to the calling procedure.

This overload lets you start a process without first creating a new Process instance. The overload is an alternative to the explicit steps of creating a new Process instance, setting the FileName member of the StartInfo property, and calling Start for the Process instance.

Starting a process by specifying its file name is similar to typing the information in the Run dialog box of the Windows Start menu. Therefore, the file name does not need to represent an executable file. It can be of any file type for which the extension has been associated with an application installed on the system. For example the file name can have a .txt extension if you have associated text files with an editor, such as Notepad, or it can have a .doc if you have associated.doc files with a word processing tool, such as Microsoft Word. Similarly, in the same way that the Run dialog box can accept an executable file name with or without the .exe extension, the .exe extension is optional in the fileName parameter. For example, you can set the fileName parameter to either "Notepad.exe" or "Notepad".

This overload does not allow command-line arguments for the process. If you need to specify one or more command-line arguments for the process, use the Process.Start or Process.Start overloads.

Unlike the other overloads, the overload of Start that has no parameters is not a static member. Use that overload when you have already created a Process instance, specified start information (including the file name), and want to start a process resource and associate it with the existing Process instance. Use one of the static overloads when you want to create a new Process component rather than start a process for an existing component. Both this overload and the overload that has no parameters allow you to specify the file name of the process resource to start.

If you have a path variable declared in your system using quotes, you must fully qualify that path when starting any process found in that location. Otherwise, the system will not find the path. For example, if c:\mypath is not in your path, and you add it using quotation marks: path = %path%;"c:\mypath", you must fully qualify any process in c:\mypath when starting it.


ASP.NET Web page and server control code executes in the context of the ASP.NET worker process on the Web server. If you use the Start method in an ASP.NET Web page or server control, the new process executes on the Web server with restricted permissions. The process does not start in the same context as the client browser, and does not have access to the user desktop.

Whenever you use Start to start a process, you might need to close it or you risk losing system resources. Close processes using CloseMainWindow or Kill.

A note about apartment states in managed threads is necessary here. When UseShellExecute is true on the process component's StartInfo property, make sure you have set a threading model on your application by setting the attribute [STAThread] on the main() method. Otherwise, a managed thread can be in an unknown state or put in the MTA state, the latter of which conflicts with UseShellExecute being true. Some methods require that the apartment state not be unknown. If the state is not explicitly set, when the application encounters such a method, it defaults to MTA, and once set, the apartment state cannot be changed. However, MTA causes an exception to be thrown when the operating system shell is managing the thread.

The following example first spawns an instance of Internet Explorer and displays the contents of the Favorites folder in the browser. It then starts some other instances of Internet Explorer and displays some specific pages or sites. Finally it starts Internet Explorer with the window being minimized while navigating to a specific site.

Imports System
Imports System.Diagnostics
Imports System.ComponentModel

Namespace MyProcessSample
   '/ <summary>
   '/ Shell for the sample.
   '/ </summary>
   Class MyProcess 
      '/ <summary>
      '/ Opens the Internet Explorer application.
      '/ </summary>
      Public Sub OpenApplication(myFavoritesPath As String)
         ' Start Internet Explorer. Defaults to the home page.
         ' Display the contents of the favorites folder in the browser.
      End Sub 'OpenApplication
      '/ <summary>
      '/ Opens urls and .html documents using Internet Explorer.
      '/ </summary>
      Sub OpenWithArguments()
         ' url's are not considered documents. They can only be opened
         ' by passing them as arguments.
         Process.Start("IExplore.exe", "")
         ' Start a Web page using a browser associated with .html and .asp files.
         Process.Start("IExplore.exe", "C:\myPath\myFile.htm")
         Process.Start("IExplore.exe", "C:\myPath\myFile.asp")
      End Sub 'OpenWithArguments
      '/ <summary>
      '/ Uses the ProcessStartInfo class to start new processes, both in a minimized 
      '/ mode.
      '/ </summary>
      Sub OpenWithStartInfo()
         Dim startInfo As New ProcessStartInfo("IExplore.exe")
         startInfo.WindowStyle = ProcessWindowStyle.Minimized
         startInfo.Arguments = ""
      End Sub 'OpenWithStartInfo
      Shared Sub Main()
         ' Get the path that stores favorite links.
         Dim myFavoritesPath As String = Environment.GetFolderPath(Environment.SpecialFolder.Favorites)
         Dim myProcess As New MyProcess()
      End Sub 'Main 
   End Class 'MyProcess
End Namespace 'MyProcessSample

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0