Custom Caret for WinForms TextBox

Question

I'm developing a custom HyperTerminal like application in a WinForms .Net 2.0 application. I have a multiline TextBox in a Panel in which you can interact with a hardware device.

My customer wants to have a custom Caret, a filled rectangle the size of one character space instead of the vertical line that is by default.

I know .Net does not provide an option to do this by default, but there must some Windows function to do it.

Answer 1

Assume a form with a textbox on it:

public partial class Form1 : Form
{
    [DllImport("user32.dll")]
    static extern bool CreateCaret(IntPtr hWnd, IntPtr hBitmap, int nWidth, int nHeight);
    [DllImport("user32.dll")]
    static extern bool ShowCaret(IntPtr hWnd);

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Shown(object sender, EventArgs e)
    {
        CreateCaret(textBox1.Handle, IntPtr.Zero, 10, textBox1.Height);
        ShowCaret(textBox1.Handle);
    }
}