c# - Change Border Color of NumericUpDown

Question

I am very new to C#, and have a question. I have been able to change the border colors of buttons and such by changing their FlatStyle to "Flat". With the NumericUpDown, I can't change the FlatStyle. I would like to still be able to use the up and down arrows, so just using something else to cover the edges will not work. Here is a simplified version of what I'm doing in my code:

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace bordertest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            BackColor = Color.Black;
            numericUpDown1.BackColor = Color.Red;
        }
    }
}

Answer 1

You can derive from NumericUpDown, add a BorderColor property, override OnPaint and draw border based on the border color.

using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
public class MyNumericUpDown : NumericUpDown
{
    private Color borderColor = Color.Blue;
    [DefaultValue(typeof(Color), "0,0,255")]
    public Color BorderColor
    {
        get { return borderColor; }
        set
        {
            if (borderColor != value)
            {
                borderColor = value;
                Invalidate();
            }
        }
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        if (BorderStyle != BorderStyle.None)
        {
            using (var pen = new Pen(BorderColor, 1))
                e.Graphics.DrawRectangle(pen,
                    ClientRectangle.Left, ClientRectangle.Top,
                    ClientRectangle.Width - 1, ClientRectangle.Height - 1);
        }
    }
}

Note: Just as a side note, this control raises paint event and if for any reason someone wants to achieve the same behavior without inheritance they can handle the Paint event and draw the border; however as a general solution and a reusable one, a derived control makes more sense.

private void numericUpDown_Paint(object sender, PaintEventArgs e)
{
    var c = (NumericUpDown)sender;
    ControlPaint.DrawBorder(e.Graphics, c.ClientRectangle,
        Color.Red, ButtonBorderStyle.Solid);
    var r = new Rectangle(1, 1, c.Width - 2, c.Height - 2);
    e.Graphics.SetClip(r);
}

FlatNumericUpDown

I've created a FlatNumericUpDown which supports BorderColor and ButtonHighlightColor. You can download or clone it:

• Repository:r-aghaei/FlatNumericUpDownExample
• Download master.zip