namespace GetWindowsVersion
{
[ StructLayout( LayoutKind.Sequential )]
public class OSVersionInfo
{
public int OSVersionInfoSize;
public int MajorVersion;
public int MinorVersion;
public int BuildNumber;
public int PlatformId;

[ MarshalAs( UnmanagedType.ByValTStr, SizeConst=128 )]
public String versionString;
}

[ StructLayout( LayoutKind.Sequential )]
public struct OSVersionInfo2
{
public int OSVersionInfoSize;
public int MajorVersion;
public int MinorVersion;
public int BuildNumber;
public int PlatformId;

[ MarshalAs( UnmanagedType.ByValTStr, SizeConst=128 )]
public String versionString;
}

public class LibWrap
{
[ DllImport( "kernel32" )]
public static extern bool GetVersionEx( [In, Out] OSVersionInfo osvi );

[ DllImport( "kernel32", EntryPoint="GetVersionEx" )]
public static extern bool GetVersionEx2( ref OSVersionInfo2 osvi );
}

public class App
{
public static void Main()
{
Console.WriteLine( "\nPassing OSVersionInfo as class" );

OSVersionInfo osvi = new OSVersionInfo();
osvi.OSVersionInfoSize = Marshal.SizeOf( osvi );

LibWrap.GetVersionEx( osvi );

Console.WriteLine( "Class size: {0} \nOperation System : {1}\nPack: {2}", osvi.OSVersionInfoSize, OpSysName(osvi.MajorVersion, osvi.MinorVersion,osvi.PlatformId),osvi.versionString);
Console.WriteLine("{0}", osvi.PlatformId);

Console.WriteLine( "\nPassing OSVersionInfo as struct" );

OSVersionInfo2 osvi2 = new OSVersionInfo2();
osvi2.OSVersionInfoSize = Marshal.SizeOf( osvi2 );

LibWrap.GetVersionEx2( ref osvi2 );
Console.WriteLine( "Static size: {0} \nOperation System : {1}\nPack: {2}", osvi2.OSVersionInfoSize, OpSysName(osvi2.MajorVersion, osvi2.MinorVersion,osvi2.PlatformId),osvi2.versionString);

}
public static String OpSysName(int MajorVersion,int MinorVersion ,int PlatformId)
{
String str_opn =String.Format("{0}.{1}",MajorVersion,MinorVersion);

switch(str_opn)
{
case "4.0":
return win95_nt40(PlatformId);
case "4.10":
return "Windows 98";
case "4.90":
return "Windows Me";
case "3.51":
return "Windows NT 3.51";
case "5.0":
return "Windwos 2000";
case "5.1":
return "Windwos XP";
case "5.2":
return "Windows Server 2003 family";
default:
return "This windows version is not distinguish!";
}
}
public static String win95_nt40(int PlatformId)
{
switch(PlatformId)
{
case 1:
return "Windows 95";
case 2:
return "Windows NT 4.0";
default:
return "This windows version is not distinguish!";
}
}
}
}