Environment.SetEnvironmentVariable Method (String, String)
Creates, modifies, or deletes an environment variable stored in the current process.
Assembly: mscorlib (in mscorlib.dll)
variable is a null reference (Nothing in Visual Basic).
variable contains a zero-length string, an initial hexadecimal zero character (0x00), or an equal sign ("=").
The length of variable or value is greater than or equal to 32,767 characters.
An error occurred during the execution of this operation.
The caller does not have the required permission to perform this operation.
If the value parameter is not empty and the environment variable named by the variable parameter does not exist, the environment variable is created and assigned the contents of value. Solely for purposes of this operation, value is considered empty if it is a null reference (Nothing in Visual Basic), contains a zero-length string, or contains an initial hexadecimal zero character (0x00).
If variable contains a non-initial hexadecimal zero character, the characters before the zero character are considered the environment variable name and all subsequent characters are ignored.
If value contains a non-initial hexadecimal zero character, the characters before the zero character are assigned to the environment variable and all subsequent characters are ignored.
If value is empty and the environment variable named by variable exists, the environment variable is deleted. If variable does not exist, no error occurs even though the operation cannot be performed.
The following example creates environment variables for the Process, User, and Machine targets, checks whether the operating system registry contains the User and Machine environment variables, then deletes the environment variables.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.