How do I get and set Environment variables in C#?

Question

How can I get Environnment variables and if something is missing, set the value?

Answer 1

Use the System.Environment class.

The methods

var value = System.Environment.GetEnvironmentVariable(variable [, Target])

and

System.Environment.SetEnvironmentVariable(variable, value [, Target])

will do the job for you.

The optional parameter Target is an enum of type EnvironmentVariableTarget and it can be one of: Machine, Process, or User. If you omit it, the default target is the current process.

Answer 2

I ran into this while working on a .NET console app to read the PATH environment variable, and found that using System.Environment.GetEnvironmentVariable will expand the environment variables automatically.

I didn't want that to happen...that means folders in the path such as '%SystemRoot%\system32' were being re-written as 'C:\Windows\system32'. To get the un-expanded path, I had to use this:

string keyName = @"SYSTEM\CurrentControlSet\Control\Session Manager\Environment\";
string existingPathFolderVariable = (string)Registry.LocalMachine.OpenSubKey(keyName).GetValue("PATH", "", RegistryValueOptions.DoNotExpandEnvironmentNames);

Worked like a charm for me.

Answer 3

This will work for an environment variable that is machine setting. For Users, just change to User instead.

String EnvironmentPath = System.Environment
                .GetEnvironmentVariable("Variable_Name", EnvironmentVariableTarget.Machine);

Answer 4

Get and Set

Get

string getEnv = Environment.GetEnvironmentVariable("envVar");

Set

string setEnv = Environment.SetEnvironmentVariable("envvar", varEnv);

Answer 5

Environment.SetEnvironmentVariable("Variable name", value, EnvironmentVariableTarget.User);

Answer 6

I could be able to update the environment variable by using the following

string EnvPath = System.Environment.GetEnvironmentVariable("PATH", EnvironmentVariableTarget.Machine) ?? string.Empty;
if (!string.IsNullOrEmpty(EnvPath) && !EnvPath .EndsWith(";"))
    EnvPath = EnvPath + ';';
EnvPath = EnvPath + @"C:\Test";
Environment.SetEnvironmentVariable("PATH", EnvPath , EnvironmentVariableTarget.Machine);