/// <summary>Creates, modifies, or deletes an environment variable stored in the current process or in the Windows operating system registry key reserved for the current user or local machine.</summary>
/// <param name="variable">The name of an environment variable.</param>
/// <param name="value">A value to assign to <paramref name="variable" />. </param>
/// <param name="target">One of the <see cref="T:System.EnvironmentVariableTarget" /> values.</param>
/// <exception cref="T:System.ArgumentNullException">
/// <paramref name="variable" /> is null. </exception>
/// <exception cref="T:System.ArgumentException">
/// <paramref name="variable" /> contains a zero-length string, an initial hexadecimal zero character (0x00), or an equal sign ("="). -or-The length of <paramref name="variable" /> is greater than or equal to 32,767 characters.-or-<paramref name="target" /> is not a member of the <see cref="T:System.EnvironmentVariableTarget" /> enumeration. -or-<paramref name="target" /> is <see cref="F:System.EnvironmentVariableTarget.Machine" /> or <see cref="F:System.EnvironmentVariableTarget.User" /> and the length of <paramref name="variable" /> is greater than or equal to 255.-or-<paramref name="target" /> is <see cref="F:System.EnvironmentVariableTarget.Process" /> and the length of <paramref name="value" /> is greater than or equal to 32,767 characters. -or-An error occurred during the execution of this operation.</exception>
/// <exception cref="T:System.NotSupportedException">
/// <paramref name="target" /> is <see cref="F:System.EnvironmentVariableTarget.User" /> or <see cref="F:System.EnvironmentVariableTarget.Machine" /> and the current operating system is Windows 95, Windows 98, or Windows Me.</exception>
/// <exception cref="T:System.Security.SecurityException">The caller does not have the required permission to perform this operation. </exception>
/// <filterpriority>1</filterpriority>
/// <PermissionSet>
/// <IPermission class="System.Security.Permissions.EnvironmentPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Unrestricted="true" />
/// <IPermission class="System.Security.Permissions.RegistryPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Unrestricted="true" />
/// <IPermission class="System.Security.Permissions.SecurityPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" version="1" Flags="UnmanagedCode" />
/// </PermissionSet>
public static void SetEnvironmentVariable(string variable, string value, EnvironmentVariableTarget target)
{
if (variable == null)
{
throw new ArgumentNullException("variable");
}
if (variable == string.Empty)
{
throw new ArgumentException("String cannot be of zero length.", "variable");
}
if (variable.IndexOf('=') != -1)
{
throw new ArgumentException("Environment variable name cannot contain an equal character.", "variable");
}
if (variable[0] == '\0')
{
throw new ArgumentException("The first char in the string is the null character.", "variable");
}
switch (target)
{
case EnvironmentVariableTarget.Process:
Environment.InternalSetEnvironmentVariable(variable, value);
break;
case EnvironmentVariableTarget.User:
if (!Environment.IsRunningOnWindows)
{
return;
}
using (RegistryKey registryKey = Registry.CurrentUser.OpenSubKey("Environment", true))
{
if (string.IsNullOrEmpty(value))
{
registryKey.DeleteValue(variable, false);
}
else
{
registryKey.SetValue(variable, value);
}
Environment.internalBroadcastSettingChange();
}
break;
case EnvironmentVariableTarget.Machine:
if (!Environment.IsRunningOnWindows)
{
return;
}
using (RegistryKey registryKey2 = Registry.LocalMachine.OpenSubKey("SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Environment", true))
{
if (string.IsNullOrEmpty(value))
{
registryKey2.DeleteValue(variable, false);
}
else
{
registryKey2.SetValue(variable, value);
}
Environment.internalBroadcastSettingChange();
}
break;
default:
throw new ArgumentException("target");
}
}