I'm trying to set a system environment variable in my application, but get an SecurityException
. I tested everything I found in google - without success.
Here is my code (note, that I'm administrator of my pc and run VS2012 as admin):
Attempt 1
new EnvironmentPermission(EnvironmentPermissionAccess.Write, "TEST1").Demand();
Environment.SetEnvironmentVariable("TEST1", "MyTest", EnvironmentVariableTarget.Machine);
Attempt 2
new EnvironmentPermission(EnvironmentPermissionAccess.Write, "TEST1").Demand();
using (var envKey = Registry.LocalMachine.OpenSubKey(@"SYSTEM\CurrentControlSet\Control\Session Manager\Environment", true))
{
Contract.Assert(envKey != null, @"HKLM\System\CurrentControlSet\Control\Session Manager\Environment is missing!");
envKey.SetValue("TEST1", "TestValue");
}
Attempt 3 Also I tried to fit out my app with administrator priviliges.
Do you have any other suggestions?
On the Windows taskbar, right-click the Windows icon and select System. In the Settings window, under Related Settings, click Advanced system settings. On the Advanced tab, click Environment Variables. Click New to create a new environment variable.
To set (or change) a environment variable, use command " set varname=value ". There shall be no spaces before and after the '=' sign. To unset an environment variable, use " set varname= ", i.e., set it to an empty string.
Environment variable is a global variable that can affect the way the running process will behave on the system.
DESCRIPTION. The setenv() function shall update or add a variable in the environment of the calling process. The envname argument points to a string containing the name of an environment variable to be added or altered. The environment variable shall be set to the value to which envval points.
The documentation tells you how to do this.
Calling
SetEnvironmentVariable
has no effect on the system environment variables. To programmatically add or modify system environment variables, add them to theHKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment
registry key, then broadcast aWM_SETTINGCHANGE
message withlParam
set to the string"Environment"
. This allows applications, such as the shell, to pick up your updates.
So, you need to write to the registry setting that you are already attempting to write to. And then broadcast a WM_SETTINGCHANGE
message as detailed above. You will need to be running with elevated rights in order for this to succeed.
Some example code:
using Microsoft.Win32;
using System;
using System.Diagnostics.Contracts;
using System.Runtime.InteropServices;
namespace ConsoleApplication1
{
class Program
{
const int HWND_BROADCAST = 0xffff;
const uint WM_SETTINGCHANGE = 0x001a;
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern bool SendNotifyMessage(IntPtr hWnd, uint Msg,
UIntPtr wParam, string lParam);
static void Main(string[] args)
{
using (var envKey = Registry.LocalMachine.OpenSubKey(
@"SYSTEM\CurrentControlSet\Control\Session Manager\Environment",
true))
{
Contract.Assert(envKey != null, @"registry key is missing!");
envKey.SetValue("TEST1", "TestValue");
SendNotifyMessage((IntPtr)HWND_BROADCAST, WM_SETTINGCHANGE,
(UIntPtr)0, "Environment");
}
}
}
}
However, whilst this code does work, the .net framework provides functionality to perform the same task much more simply.
Environment.SetEnvironmentVariable("TEST1", "TestValue",
EnvironmentVariableTarget.Machine);
The documentation for the three argument Environment.SetEnvironmentVariable
overload says:
If target is EnvironmentVariableTarget.Machine, the environment variable is stored in the HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Environment key of the local computer's registry. It is also copied to all instances of File Explorer. The environment variable is then inherited by any new processes that are launched from File Explorer.
If target is User or Machine, other applications are notified of the set operation by a Windows WM_SETTINGCHANGE message.
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