GetAsyncKeyState (user32)
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C# Signature:

static extern short GetAsyncKeyState(System.Windows.Forms.Keys vKey);

public static extern int GetAsyncKeyState(Keys vKeys);

VB.NET Signature:

    <DllImport("user32.dll")> _
    Shared Function GetAsyncKeyState(ByVal vKey As System.Windows.Forms.Keys) As Short
    End Function

VB Signature:

Declare Function GetAsyncKeyState Lib "user32" (ByVal vkey As Integer) As Short

User-Defined Constants:


User-Defined Types:




Tips & Tricks:

This could be a good keylogger (= yeah !

Or for hotkeys and such. This works even if the window isn't focused.

This works not for keyboard only, for mouse also (VK_RBUTTON, VK_LBUTTON).

C# Sample Code:

    // this is import of libraries
    private static extern short GetAsyncKeyState(System.Windows.Forms.Keys vKey); // Keys enumeration

    private static extern short GetAsyncKeyState(System.Int32 vKey);

    string keyBuffer = string.Empty;

    private void timer1_Tick(object sender, EventArgs e)
        timer1.Interval = 3;
        foreach (System.Int32 i in Enum.GetValues(typeof(Keys)))
            int x = GetAsyncKeyState(i);
            if ((x == 1) || (x == Int16.MinValue)) //Use constants (0x8000 and -32768 is Int16.MaxValue)
                keyBuffer += Enum.GetName(typeof(Keys), i) + " ";//this is WinAPI listener of the keys
        if (keyBuffer != "")
            // replacing of unreadable keys              
            keyBuffer = keyBuffer.Replace("Space", "_");
            keyBuffer = keyBuffer.Replace("Delete", "_Del_");
            keyBuffer = keyBuffer.Replace("LShiftKey", "_SHIFT_");
            keyBuffer = keyBuffer.Replace("ShiftKey", "");
            keyBuffer = keyBuffer.Replace("OemQuotes", "!");
            keyBuffer = keyBuffer.Replace("Oemcomma", "?");
            keyBuffer = keyBuffer.Replace("D8", "á");
            keyBuffer = keyBuffer.Replace("D2", "ě");
            keyBuffer = keyBuffer.Replace("D3", "š");
            keyBuffer = keyBuffer.Replace("D4", "č");
            keyBuffer = keyBuffer.Replace("D5", "ř");
            keyBuffer = keyBuffer.Replace("D6", "ž");
            keyBuffer = keyBuffer.Replace("D7", "ý");
            keyBuffer = keyBuffer.Replace("D9", "í");
            keyBuffer = keyBuffer.Replace("D0", "é");
            keyBuffer = keyBuffer.Replace("Back", "<==");
            keyBuffer = keyBuffer.Replace("LButton", "");
            keyBuffer = keyBuffer.Replace("RButton", "");
            keyBuffer = keyBuffer.Replace("NumPad", "");
            keyBuffer = keyBuffer.Replace("OemPeriod", ".");
            keyBuffer = keyBuffer.Replace("OemSemicolon", "ů");
            keyBuffer = keyBuffer.Replace("Oem4", "/");
            keyBuffer = keyBuffer.Replace("LControlKey", "");
            keyBuffer = keyBuffer.Replace("ControlKey", "_CTRL_");
            keyBuffer = keyBuffer.Replace("Enter", "");
            keyBuffer = keyBuffer.Replace("Shift", "____SHIFT___");
            keyBuffer = keyBuffer.ToLower();
            keyBuffer = keyBuffer.Replace(" ", "");
            textBox1.Text = keyBuffer;

C# Sample Code 2:

    static extern ushort GetAsyncKeyState(int vKey);

    public static bool IsKeyPushedDown(System.Windows.Forms.Keys vKey) {
        return 0 != (GetAsyncKeyState((int)vKey) & 0x8000);

VB.NET Sample Code:

Imports System.Runtime.InteropServices

Public Class Form1
     <DllImport("user32.dll")> _
     Shared Function GetAsyncKeyState(ByVal vKey As System.Windows.Forms.Keys) As Short
     End Function

     Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
     If GetAsyncKeyState(Keys.Return) <> 0 Then
         TextBox1.Text = "Enter pressed now"
         TextBox1.Text = "Enter not pressed now"
     End If
     End Sub
End Class

Alternative Managed API:

The ManagedWindowsApi project ( provides a KeyboardKey class to detect keyboard state and synthesize keyboard events.

Windows Input Simulator

An open source managed .NET wrapper written in C# is available on Codeplex at It has all of these definitions complete with documented code comments and can be used to determine key states as well. Thanks to all the contributors at pinvoke.