Try this one
Using System.Runtime.InteropServices
byte VK_KEY = 0x41; //"A" key in this instance
const int KEYEVENTF_KEYUP = 0x2;
const int KEYEVENTF_KEYDOWN = 0x0;
keybd_event(VK_KEY, 0, KEYEVENTF_KEYDOWN, 0);//press tab
keybd_event(VK_KEY, 0, KEYEVENTF_KEYUP, 0);//release tab
[DllImport("coredll.dll", SetLastError = true)]
static extern void keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);