来自Chriz Yuen的博客

介绍了两个新的环境属性 Environment.Is64BitOperatingSystem; Environment.Is64BitProcess;

当你使用这两种属性时请小心。 在Windows 7 64位机器上测试

//Workspace: Target Platform x86
Environment.Is64BitOperatingSystem True
Environment.Is64BitProcess False

//Workspace: Target Platform x64
Environment.Is64BitOperatingSystem True
Environment.Is64BitProcess True

//Workspace: Target Platform Any
Environment.Is64BitOperatingSystem True
Environment.Is64BitProcess True

我使用以下版本:

    public static bool Is64BitSystem()
    {
        if (Directory.Exists(Environment.GetEnvironmentVariable("Program Files (x86)"))) return true;
        else return false;
    }

完整的答案是这样的(摘自stefan-mg, ripper234和BobbyShaftoe的答案):

    [DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool IsWow64Process([In] IntPtr hProcess, [Out] out bool lpSystemInfo);

    private bool Is64Bit()
    {
        if (IntPtr.Size == 8 || (IntPtr.Size == 4 && Is32BitProcessOn64BitProcessor()))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    private bool Is32BitProcessOn64BitProcessor()
    {
        bool retVal;

        IsWow64Process(Process.GetCurrentProcess().Handle, out retVal);

        return retVal;
    } 

首先检查您是否处于64位进程中。如果不是，检查32位进程是否是Wow64Process。

使用dotPeek有助于了解框架是如何实际执行的。考虑到这一点，以下是我的想法:

public static class EnvironmentHelper
{
    [DllImport("kernel32.dll")]
    static extern IntPtr GetCurrentProcess();

    [DllImport("kernel32.dll")]
    static extern IntPtr GetModuleHandle(string moduleName);

    [DllImport("kernel32")]
    static extern IntPtr GetProcAddress(IntPtr hModule, string procName);

    [DllImport("kernel32.dll")]
    static extern bool IsWow64Process(IntPtr hProcess, out bool wow64Process);

    public static bool Is64BitOperatingSystem()
    {
        // Check if this process is natively an x64 process. If it is, it will only run on x64 environments, thus, the environment must be x64.
        if (IntPtr.Size == 8)
            return true;
        // Check if this process is an x86 process running on an x64 environment.
        IntPtr moduleHandle = GetModuleHandle("kernel32");
        if (moduleHandle != IntPtr.Zero)
        {
            IntPtr processAddress = GetProcAddress(moduleHandle, "IsWow64Process");
            if (processAddress != IntPtr.Zero)
            {
                bool result;
                if (IsWow64Process(GetCurrentProcess(), out result) && result)
                    return true;
            }
        }
        // The environment must be an x86 environment.
        return false;
    }
}

使用示例:

EnvironmentHelper.Is64BitOperatingSystem();

这只是Bruno Lopez上面建议的一个实现，但适用于Win2k +所有的WinXP服务包。我只是想把它贴出来这样别人就不用亲手卷了。(本可以作为评论发布，但我是一个新用户!)

[DllImport("kernel32", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
public extern static IntPtr LoadLibrary(string libraryName);

[DllImport("kernel32", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
public extern static IntPtr GetProcAddress(IntPtr hwnd, string procedureName);

private delegate bool IsWow64ProcessDelegate([In] IntPtr handle, [Out] out bool isWow64Process);

public static bool IsOS64Bit()
{
    if (IntPtr.Size == 8 || (IntPtr.Size == 4 && Is32BitProcessOn64BitProcessor()))
    {
        return true;
    }
    else
    {
        return false;
    }
}

private static IsWow64ProcessDelegate GetIsWow64ProcessDelegate()
{
  IntPtr handle = LoadLibrary("kernel32");

  if ( handle != IntPtr.Zero)
  {
    IntPtr fnPtr = GetProcAddress(handle, "IsWow64Process");

    if (fnPtr != IntPtr.Zero)
    {
      return (IsWow64ProcessDelegate)Marshal.GetDelegateForFunctionPointer((IntPtr)fnPtr, typeof(IsWow64ProcessDelegate));
    }
  }

  return null;
}

private static bool Is32BitProcessOn64BitProcessor()
{
  IsWow64ProcessDelegate fnDelegate = GetIsWow64ProcessDelegate();

  if (fnDelegate == null)
  {
    return false;
  }

  bool isWow64;
  bool retVal = fnDelegate.Invoke(Process.GetCurrentProcess().Handle, out isWow64);

  if (retVal == false)
  {
    return false;
  }

  return isWow64;
}

最快的方式:

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

注意:这是非常直接的，只有当程序不强制作为32位进程执行时(例如，在项目设置中通过<Prefer32Bit>true</Prefer32Bit>)，才能在64位上正确工作。