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Process.Start Method (String, String, SecureString, String)

Starts a process resource by specifying the name of an application, a user name, a password, and a domain and associates the resource with a new Process component.

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

public static Process Start(
	string fileName,
	string userName,
	SecureString password,
	string domain


Type: System.String

The name of an application file to run in the process.

Type: System.String

The user name to use when starting the process.

Type: System.Security.SecureString

A SecureString that contains the password to use when starting the process.

Type: System.String

The domain to use when starting the process.

Return Value

Type: System.Diagnostics.Process
A new Process component that is associated with the process resource, or null if no process resource is started (for example, if an existing process is reused).


No file name was specified.


fileName is not an executable (.exe) file.


There was an error in opening the associated file.


The process object has already been disposed.

Use this overload to create a new process and its primary thread by specifying its file name, user name, password, and domain. The new process then runs the specified executable file in the security context of the specified credentials (user, domain, and password).


When the executable file is located on a remote drive, you must identify the network share by using a uniform resource identifier (URI), not a linked drive letter.

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 null 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, UserName, Password, and Domain properties of the StartInfo property, and calling Start for the Process instance.

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". If the fileName parameter represents an executable file, the arguments parameter might represent a file to act upon, such as the text file in Notepad.exe myfile.txt.


The file name must represent an executable file in the Start overloads that have userName, password, and domain parameters.

The following code example shows the use of this overload to start an executable file and also demonstrates the throwing of a Win32Exception when an attempt is made to start an application associated with a nonexecutable file.

// This sample requires a text.txt file and a HelloWorld.exe file in the  
// My Documents folder to successfully execute. 
using System;
using System.Diagnostics;
using System.Security;
using System.ComponentModel;

namespace StartDemo
    class Program
        static void Main(string[] args)
            Console.WriteLine("Enter your domain.");
            string domain = Console.ReadLine();
            Console.WriteLine("Enter you user name.");
            string uname = Console.ReadLine();
            Console.WriteLine("Enter your password (Caution, password won't be hidden).");
            SecureString password = new SecureString();
            foreach (char c in Console.ReadLine())
            string path = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + "\\";
            Process.Start(path + "HelloWorld.exe", uname, password, domain);
                // The following call to Start succeeds.
                Process.Start(path + "Text.txt");
                // Attempting to start in a shell using this Start overload fails. 
                // The following call to Start results in the following error: 
                // The specified executable is not a valid Win32 application.
                Process.Start(path + "Text.txt", uname, password, domain);
            catch (Win32Exception ex)

  • LinkDemand 

    for full trust for the immediate caller. This member cannot be used by partially trusted code.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

Supported in: 3.5, 3.0, 2.0