How can I retrieve the values from window of class "ThunderRT6ListBox" using user32.dll in c#

Question

I am trying to retrieve information from extern desktop aplication in Windows.

I know how extract the text from Textboxes (class "Edit") but I don't know how extract the values from controls with class name "ThunderRT6ListBox" and "ThunderRT6ComboBox". How can I do that?

I have this code to extract the text from the textbox:

public static class ModApi
{
    [DllImport("user32.dll", EntryPoint = "FindWindowA", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
    public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    public static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);

    [DllImport("user32.dll", EntryPoint = "SendMessageTimeout", SetLastError = true, CharSet = CharSet.Auto)]
    public static extern uint SendMessageTimeoutText(IntPtr hWnd, int Msg, int countOfChars, StringBuilder text, uint flags, uint uTImeoutj, uint result);

    [DllImport("user32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
    static internal extern bool EnumChildWindows(IntPtr hWndParent, funcCallBackChild funcCallBack, IntPtr lParam);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)]
    static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, StringBuilder lParam);
    const int LB_GETCOUNT = 0x018B;
    const int LB_GETTEXT = 0x0189;

    public static string GetText(IntPtr hwnd)
    {
        var text = new StringBuilder(1024);
        if (SendMessageTimeoutText(hwnd, 0xd, 1024, text, 0x2, 1000, 0) != 0)
        {
            return text.ToString();
        }

        return "";
    }        
}


public foo()
{
     IntPtr value = new IntPtr(0x019C086A); //ID locate using Spy++
     String caption = ModApi.GetText(value);
}

UPDATE 1:

The way to read from ListBox:

    public static List<string> GetListBoxContents(IntPtr listBoxHwnd)
    {
        int cnt = (int)SendMessage(listBoxHwnd, LB_GETCOUNT, IntPtr.Zero, null);
        List<string> listBoxContent = new List<string>();
        for (int i = 0; i < cnt; i++)
        {
            StringBuilder sb = new StringBuilder(256);
            IntPtr getText = SendMessage(listBoxHwnd, LB_GETTEXT, (IntPtr)i, sb);
            listBoxContent.Add(sb.ToString());
        }
        return listBoxContent;
    }

UPDATE 2:

The way to read from ComboBox:

    public static List<string> GetComboBoxContents(IntPtr cbBoxHwnd)
    {
        int cnt = (int)SendMessage(cbBoxHwnd, CB_GETCOUNT, IntPtr.Zero, null);
        List<string> listBoxContent = new List<string>();
        for (int i = 0; i < cnt; i++)
        {
            //int txtLength = SendMessage(cbBoxHwnd, CB_GETLBTEXTLEN, i, 0); 
            StringBuilder sb = new StringBuilder(256);
            IntPtr getText = SendMessage(cbBoxHwnd, CB_GETLBTEXT, (IntPtr)i, sb);
            listBoxContent.Add(sb.ToString());
        }
        return listBoxContent;
    }

Answer 1

You're dealing with a VB6 application from eons ago. "Thunder" was the internal name for the VB product/project (trivial side note).

You're closer than you realize. If you have the HWND to the control, and I think you do:

1. Call SendMessage with that HWND and the message LB_GETCOUNT to get the number of items in the list.
2. For each index, call SendMessage with LB_GETTEXTLEN and the current item index to get the length of the text, then allocate a buffer accordingly.
3. Call SendMessage again, this time using LB_GETTEXT message, same item index (zero-based), and the reference to your buffer, and that should get you each item's text.

You might consider one more declaration/alias to SendMessage that just returns an int, which should make some of these calls simpler.

If I get a chance, I will clean this up a bit later with a more specific code example (or at least pseudocode), but I get the impression you're very much on the right track already and may only need this basic description to get the rest of the way.

Good luck!