.NET Framework Standard Library Annotated Reference, Volume 1: Base Class Library and Extended Numerics Library

Example

using System;
using System.Security;
using System.Security.Permissions;

[assembly:EnvironmentPermissionAttribute(
                SecurityAction.RequestMinimum,
                Read="COMPUTERNAME;USERNAME")]

namespace Samples
{
  public class SecurityActionSample
  {
    public static void Main()
    {
      string[] v = {"USERNAME", "COMPUTERNAME"};
      foreach(string s in v)
        Console.WriteLine("Variable {0} Value: {1}",
                 s,
                 Environment.GetEnvironmentVariable(s));

    }
  }
}

The output is

Variable USERNAME Value: damien
Variable COMPUTERNAME Value: PROJECT42