Using IntPtr

IntPtr used to keep native handles in dotNET. Because of its structure it is important to what size it is. This is a our trick, checking size of IntPtr. IntPtr will be 8 if application is running on a 64bit OS, otherwise in 32bit OS it will be 4.

C# Code

if(IntPtr.Size == 8) 
{
	// 64 bit machine
} 
else if(IntPtr.Size == 4) 
{
	// 32 bit machine
}

VB.NET Code

If IntPtr.Size = 8 Then

	' 64 bit machine

ElseIf IntPtr.Size = 4 Then

	' 32 bit machine

End If

Other methods

Another way is checking for the existence of the "ProgramFiles(x86)" environment variable. This is not a recomended way but anyway you can use it!

public bool Is64bitOS
{
    get { return (Environment.GetEnvironmentVariable("ProgramFiles(x86)") != null); }
}

public string ProgramFilesX86
{
    get
    {
        string programFiles = Environment.GetEnvironmentVariable("ProgramFiles(x86)");
        if (programFiles == null)
        {
            programFiles = Environment.GetEnvironmentVariable("ProgramFiles");
        }

        return programFiles;
    }
}

The Is64bitOS property will be true if application is ruunig on a 64bit OS.

Another way is GetNativeSystemInfo windows API. Because it is an API and needs PInvode it is not recommended but it is a reliable way.