Use this overload to start a process resource by specifying a System.Diagnostics.ProcessStartInfo instance. The overload associates the resource with a new System.Diagnostics.Process component. If the process is already running, no additional process resource is started. Instead, the existing process resource is reused and no new System.Diagnostics.Process component is created. In such a case, instead of returning a new System.Diagnostics.Process component, Process.Start returns null to the calling procedure.

This overload lets you start a process without first creating a new System.Diagnostics.Process instance. Using this overload with a System.Diagnostics.ProcessStartInfo parameter is an alternative to the explicit steps of creating a new System.Diagnostics.Process instance, setting its Process.StartInfo properties, and calling Process.Start for the System.Diagnostics.Process instance.

Using a System.Diagnostics.ProcessStartInfo instance as the parameter lets you call Process.Start with the most control over what is passed into the call to start the process. If you need to pass only a file name or a file name and arguments, it is not necessary to create a new System.Diagnostics.ProcessStartInfo instance, although that is an option. The only Process.StartInfo property that must be set is the ProcessStartInfo.FileName property. The ProcessStartInfo.FileName property 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 that is installed on the system. For example, the ProcessStartInfo.FileName property can have a .txt extension if you have associated text files with an editor, such as Notepad, or it can have a .doc extension if you have associated.doc files with a word processing tool, such as Microsoft Word.

You can start a ClickOnce application by specifying the location (for example, a Web address) from which you originally installed the application. Do not start a ClickOnce application by specifying its installed location on your hard drive.

If the ProcessStartInfo.UserName and ProcessStartInfo.Password properties of the Process.StartInfo instance are set, the unmanaged CreateProcessWithLogonW function is called, which starts the process in a new window even if the ProcessStartInfo.CreateNoWindow property value is true or the ProcessStartInfo.WindowStyle property value is ProcessWindowStyle.Hidden.

Unlike the other overloads, the overload of Process.Start that has no parameters is not a static member. Use that overload when you have already created a System.Diagnostics.Process instance, specified start information (including the file name), and want to start a process resource and associate it with the existing System.Diagnostics.Process instance. Use one of the static overloads when you want to create a new System.Diagnostics.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 start information for the process resource by using a System.Diagnostics.ProcessStartInfo instance.

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.

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

A note about apartment states in managed threads is necessary here. When ProcessStartInfo.UseShellExecute is true on the startInfo parameter, 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 ProcessStartInfo.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.

Namespace: System.Diagnostics
Assembly: System (in System.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0