GroupBox 를 상속받아 OnPaint 함수를 오버라이딩 하면

GroupBox의 색상을 변경할수 있습니다.

전체소스

       WATGroupBoxDlg.zip

주요 소스

       WATGroupBox myGroupBox = new WATGroupBox();
       
        public frmMain()
        {
            InitializeComponent();
            myGroupBox.Text = "GroupBox1";
            myGroupBox.BorderColor = Color.Black;
            this.Controls.Add(myGroupBox);
        }

        private void btnRED_Click(object sender, EventArgs e)
        {
            myGroupBox.BorderColor = Color.Red;

        }

        private void btnBLUE_Click(object sender, EventArgs e)
        {
            myGroupBox.BorderColor = Color.Blue;
        }

        private void btnDelBorder_Click(object sender, EventArgs e)
        {
            myGroupBox.BorderColor = System.Drawing.SystemColors.Control;
        }
    }

    public class WATGroupBox : GroupBox
    {
        private Color borderColor;
        public Color BorderColor
        {
            get { return this.borderColor; }

            set { this.borderColor = value;
                this.Invalidate();
            }

        }

        public WATGroupBox()
        {
            this.borderColor = Color.Black;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            Size tSize = TextRenderer.MeasureText(this.Text, this.Font);
            Rectangle borderRect = e.ClipRectangle;
            borderRect.Y += tSize.Height / 2;
            borderRect.Height -= tSize.Height / 2;
            ControlPaint.DrawBorder(e.Graphics, borderRect, this.borderColor, ButtonBorderStyle.Solid);

            Rectangle textRect = e.ClipRectangle;
            textRect.X += 6;
            textRect.Width = tSize.Width;
            textRect.Height = tSize.Height;
            e.Graphics.FillRectangle(new SolidBrush(this.BackColor), textRect);
            e.Graphics.DrawString(this.Text, this.Font, new SolidBrush(this.ForeColor), textRect);

        }

    }