GetKeyState() not evaluating correctly

Question

the GetKeyState() in my code is not evaluating correctly .. when i use this :

 bool ctrlDown = GetKeyState(VK_LCONTROL) != 0 || GetKeyState(VK_RCONTROL) != 0;

in my code its not coming back with the correct info.. its fired on all key events and its being evaluated as true even when other keys are pressed.. can anyone see anything im doing wrong in this code ?

i load it up here :

    [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
    public static extern short GetKeyState(int nVirtKey);

Then i call the "VK_LCONTROL & VK_RCONTROL" var's and fill them :

    public const int VK_LCONTROL = 0xA2;
    public const int VK_RCONTROL = 0xA3;

and then i call it in this function:

private int KbHookProc(int nCode, IntPtr wParam, IntPtr lParam)
    {
        var hookStruct = (KbLLHookStruct)Marshal.PtrToStructure(lParam, typeof(KbLLHookStruct));

        bool ctrlDown = GetKeyState(VK_LCONTROL) != 0 || GetKeyState(VK_RCONTROL) != 0;

        if (nCode >= 0 && wParam == (IntPtr)WM_KEYUP && hookStruct.vkCode == 0x56 && ctrlDown == true)
        {

                MessageBox.Show("Message : KEY UP");
                ComboHit = false;
        }

        // Pass to other keyboard handlers. Makes the Ctrl+V pass through.
        return CallNextHookEx(_hookHandle, nCode, wParam, lParam);        
    }

when i check so see what the " GetKeyState(VK_LCONTROL) " is returning .. its alternates back and forth between 0 & 1, i knwo that MS says it should do this : "Retrieves the status of the specified virtual key. The status specifies whether the key is up, down, or toggled (on, off—alternating each time the key is pressed). "

why would i want this ?.. and can i make it evaluate the keys up or down position accurately ?

Don't use != 0. Use < 0 to detect that the key is down. – Hans Passant Jan 24 '12 at 23:19 — Hans Passant, Jan 24 '12 at 23:19

score 9 · Answer 1 · answered Jan 24 '12 at 23:15

9

To test if a key is down, you need to check the high order bit:

(GetKeyState(vk) & 0x8000)

answered Jan 24 '12 at 23:15

jdigital

11,926
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1

can you show this working please.. i dont knwo what you mean .. im sorry im new to C# – Canada_Goose Jan 25 '12 at 00:09

Chris Shain · Answer 2 · 2012-01-25T04:12:19.960

1

Why not just use Control.ModifierKeys?

Something like this?

public partial class myForm : Form
{
    public myForm()
    {
        InitializeComponent();
    }

    private void myForm_Load(object sender, EventArgs e)
    {
        KeyPreview = true;
        KeyUp += (s, ek) =>
                     {
                         if (ek.KeyCode == Keys.V && ModifierKeys.HasFlag(Keys.Control))
                             MessageBox.Show("Yerp, it done happened");
                     };
    }
}

edited Jan 25 '12 at 04:12

answered Jan 24 '12 at 23:16

Chris Shain

50,833
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Do you need to fire an event *when the key is released*, or *only allow the event to fire when the key is up* – Chris Shain Jan 25 '12 at 00:57
i need to know if both the CTRL + V have been pressed, and then only fire when the player releases the buttons. – Canada_Goose Jan 25 '12 at 03:09

score 0 · Answer 3 · edited May 23 '17 at 12:25

0

What exactly are you trying to do ? I think perhaps you could take a look at the GetKeyboardState method

https://stackoverflow.com/a/709641/55774

edited May 23 '17 at 12:25

Community

1
1

answered Jan 24 '12 at 23:16

Frederik Gheysels

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ultimately using the code i put in there im trying to check for and stop the ctrl + V on the keyboard. – Canada_Goose Jan 25 '12 at 00:07

GetKeyState() not evaluating correctly

3 Answers3