Customtextbox not adding from designer

Question

Hello ,

i recently asked a question in https://learn.microsoft.com/en-us/answers/questions/1406472/textbox-as-textboxcolumn
and @gekka suggested a solution which works . I had modified some part of it according to my requirement but after cleaning and rebuilding multiple times it can not be drop from the toolbar to the form . i am not from the visual studio design . Am i missing something or it is a bug . Please help .
modifications are

1. can't take more than specified characters
2. should have backcolor according to the containing form when dropped on it
3. should change backcolor when gets focused
4. should change back to original color

namespace Pankajtripathi
{
    public partial class CustomTextBox : TextBox
    {
        private int maxCharacters;

        public int MaxCharacters
        {
            get { return maxCharacters; }
            set
            {
                maxCharacters = value;
                Text = Text.Length > maxCharacters ? Text.Substring(0, maxCharacters) : Text;
            }
        }

        public CustomTextBox()
        {
            CustomTextBoxWork.AttachKeyEvent(this);
        }
    }

    class CustomTextBoxWork
    {
        private static Color originalBackColor;

        public static void AttachKeyEvent(TextBox txb)
        {
            txb.KeyDown += Txb_KeyDown;
            txb.LostFocus += Txb_LostFocus;
            originalBackColor = txb.Parent.BackColor; // Set the originalBackColor to the parent's back color
        }

        private static void Txb_KeyDown(object sender, KeyEventArgs e)
        {
            var txb = (TextBox)sender;
            if (e.KeyCode == Keys.Escape)
            {
                txb.Text = "";
            }
            else if (e.KeyCode == Keys.Enter)
            {
                txb.BackColor = Color.Yellow; // Change the back color to a different color when Enter is pressed
                Control ctl = txb;
                while (ctl.Parent != null)
                {
                    var next = ctl.Parent.GetNextControl(ctl, true);
                    if (next != null)
                    {
                        next.Focus();
                        e.SuppressKeyPress = true;
                        e.Handled = true;
                        return;
                    }
                    ctl = ctl.Parent;
                }
            }
        }

        private static void Txb_LostFocus(object sender, EventArgs e)
        {
            var txb = (TextBox)sender;
            txb.BackColor = originalBackColor; // Revert back to the original back color (parent's back color) when focus is lost
        }
    }
}

Answer 1

The new textbox object does not have yet a parent, therefore txb.Parent.BackColor does not work.

Try to remove the originalBackColor member. In Txb_LostFocus you can do this: txb.BackColor = txb.Parent.BackColor, or use another appropriate colour.