Programming Forums > Application Development > C#

lectricpharaoh · Mar 21st, 2008, 9:44 PM

Here is a simple console application I whipped up to demonstrate:

 C# Syntax (Toggle Plain Text) 
using System.Runtime.InteropServices;
using System.Windows.Forms;
 
namespace YourNamespaceHere
{
  class Program
  {
    [DllImport("user32.dll")]
    static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);
 
    static void Main(string[] args)
    {
      keybd_event((byte)Keys.H, 0, 0, 0);
      keybd_event((byte)Keys.H, 0, 0x7F, 0);
      keybd_event((byte)Keys.E, 0, 0, 0);
      keybd_event((byte)Keys.E, 0, 0x7F, 0);
      keybd_event((byte)Keys.L, 0, 0, 0);
      keybd_event((byte)Keys.L, 0, 0x7F, 0);
      keybd_event((byte)Keys.L, 0, 0, 0);
      keybd_event((byte)Keys.L, 0, 0x7F, 0);
      keybd_event((byte)Keys.O, 0, 0, 0);
      keybd_event((byte)Keys.O, 0, 0x7F, 0);
    }
  }
}
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace YourNamespaceHere
{
  class Program
  {
    [DllImport("user32.dll")]
    static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);

    static void Main(string[] args)
    {
      keybd_event((byte)Keys.H, 0, 0, 0);
      keybd_event((byte)Keys.H, 0, 0x7F, 0);
      keybd_event((byte)Keys.E, 0, 0, 0);
      keybd_event((byte)Keys.E, 0, 0x7F, 0);
      keybd_event((byte)Keys.L, 0, 0, 0);
      keybd_event((byte)Keys.L, 0, 0x7F, 0);
      keybd_event((byte)Keys.L, 0, 0, 0);
      keybd_event((byte)Keys.L, 0, 0x7F, 0);
      keybd_event((byte)Keys.O, 0, 0, 0);
      keybd_event((byte)Keys.O, 0, 0x7F, 0);
    }
  }
}

I did two things here: first, I used the System.Windows.Forms.Keys enumeration; this is basically the .NET version of the virtual-key constants. You need to cast them to byte first, and (if you're creating a console app, rather than a Windows forms app) add a reference in your project. To add a reference, right-click the project name in the Solution Explorer, say 'add reference', and on the .NET tab, there will be one for System.Windows.Forms. You need to do this before the matching using directive will work. If you're creating a forms app, the reference will already be there, and the using directive will too for any forms-derived classes you create.

The second thing I did was to use the constant 0x7F. This is simply the value of the KEYEVENTF_KEYUP constant. Remember that each 'key down' event needs to be matched with a corresponding 'key up' event, or the system will think a key is still being held down.

Anyways, if you create a new console application, and copy-paste my code above in, it should work fine (after you add the reference, of course). To run it, don't do it from the IDE. Rather, open up a command window (Start -> Run -> type 'cmd' and hit ENTER), navigate to the directory where your program executable is, and run it. You should get output similar to the following:

(Toggle Plain Text)

C:\PathToYourExecutable>NameOfYourExecutable

C:\PathToYourExecutable>hello

The red text is what you type at the prompt. Hit ENTER, and the prompt will re-appear with the word 'hello' typed in already (green text). This is because the program simulated the keystrokes, and they were still in the buffer.

crawforddavid2006 · Mar 21st, 2008, 10:57 PM

again, thankyou, that worked perfectly. also thank you for taking the time to explain what was going on.

lectricpharaoh · Mar 22nd, 2008, 5:20 AM

Quote:

Originally Posted by crawforddavid2006

again, thankyou, that worked perfectly. also thank you for taking the time to explain what was going on.

Glad to see it's working. However, I have a suggestion for you. Assuming you're creating a class to simulate input (and if you are, you can combine the mouse and keyboard simulation in the same class), you might want to 'wrap' the call to keybd_event() and have your public method use the Keys enumeration directly:

 C# Syntax (Toggle Plain Text) 
public static class VirtualKeyboard
{
  [DllImport("user32.dll")] static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);
 
  public static KeyDown(System.Windows.Forms.Keys key)
  {
    keybd_event((byte)key, 0, 0, 0);
  }
 
 
  public static KeyUp(System.Windows.Forms.Keys key)
  {
    keybd_event((byte)key, 0, 0x7F, 0);
  }
}
public static class VirtualKeyboard
{
  [DllImport("user32.dll")] static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);

  public static KeyDown(System.Windows.Forms.Keys key)
  {
    keybd_event((byte)key, 0, 0, 0);
  }


  public static KeyUp(System.Windows.Forms.Keys key)
  {
    keybd_event((byte)key, 0, 0x7F, 0);
  }
}

Doing it like this has three advantages. First, you don't need to port in the virtual key constants; you can use the ones in the System.Windows.Forms.Keys enumeration. Second, by using an enum, the calling code can only simulate keys for which there is a defined value (no passing in random numeric values). Third, it's clearer because there are two methods that take a single parameter, rather than one method with four (arguably more obscure) parameters. I mean, knowing the names and parameters of those two methods there makes it pretty clear what they do.

Mar 21st, 2008, 9:44 PM	#11
lectricpharaoh SEXY SHOELESS GOD OF WAR! Join Date: Jun 2005 Location: Wet west coast of Canada Posts: 1,198 Rep Power: 5	Re: Left Mouse Click Here is a simple console application I whipped up to demonstrate: C# Syntax (Toggle Plain Text) using System.Runtime.InteropServices; using System.Windows.Forms; namespace YourNamespaceHere { class Program { [DllImport("user32.dll")] static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo); static void Main(string[] args) { keybd_event((byte)Keys.H, 0, 0, 0); keybd_event((byte)Keys.H, 0, 0x7F, 0); keybd_event((byte)Keys.E, 0, 0, 0); keybd_event((byte)Keys.E, 0, 0x7F, 0); keybd_event((byte)Keys.L, 0, 0, 0); keybd_event((byte)Keys.L, 0, 0x7F, 0); keybd_event((byte)Keys.L, 0, 0, 0); keybd_event((byte)Keys.L, 0, 0x7F, 0); keybd_event((byte)Keys.O, 0, 0, 0); keybd_event((byte)Keys.O, 0, 0x7F, 0); } } } using System.Runtime.InteropServices; using System.Windows.Forms; namespace YourNamespaceHere { class Program { [DllImport("user32.dll")] static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo); static void Main(string[] args) { keybd_event((byte)Keys.H, 0, 0, 0); keybd_event((byte)Keys.H, 0, 0x7F, 0); keybd_event((byte)Keys.E, 0, 0, 0); keybd_event((byte)Keys.E, 0, 0x7F, 0); keybd_event((byte)Keys.L, 0, 0, 0); keybd_event((byte)Keys.L, 0, 0x7F, 0); keybd_event((byte)Keys.L, 0, 0, 0); keybd_event((byte)Keys.L, 0, 0x7F, 0); keybd_event((byte)Keys.O, 0, 0, 0); keybd_event((byte)Keys.O, 0, 0x7F, 0); } } } I did two things here: first, I used the `System.Windows.Forms.Keys` enumeration; this is basically the .NET version of the virtual-key constants. You need to cast them to `byte` first, and (if you're creating a console app, rather than a Windows forms app) add a reference in your project. To add a reference, right-click the project name in the Solution Explorer, say 'add reference', and on the .NET tab, there will be one for `System.Windows.Forms`. You need to do this before the matching `using` directive will work. If you're creating a forms app, the reference will already be there, and the `using` directive will too for any forms-derived classes you create. The second thing I did was to use the constant 0x7F. This is simply the value of the `KEYEVENTF_KEYUP` constant. Remember that each 'key down' event needs to be matched with a corresponding 'key up' event, or the system will think a key is still being held down. Anyways, if you create a new console application, and copy-paste my code above in, it should work fine (after you add the reference, of course). To run it, don't do it from the IDE. Rather, open up a command window (Start -> Run -> type 'cmd' and hit ENTER), navigate to the directory where your program executable is, and run it. You should get output similar to the following: (Toggle Plain Text) C:\PathToYourExecutable>NameOfYourExecutable C:\PathToYourExecutable>hello C:\PathToYourExecutable>NameOfYourExecutable C:\PathToYourExecutable>hello The red text is what you type at the prompt. Hit ENTER, and the prompt will re-appear with the word 'hello' typed in already (green text). This is because the program simulated the keystrokes, and they were still in the buffer. __________________ And once again, Probability proves itself willing to sneak into a back alley and service Drama as would a copper-piece harlot. - Vaarsuvius, Order of the Stick

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Programming Forums > Application Development > C#

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