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[ToolboxBitmap(typeof(ComboBox))] class ComboBoxEx : ComboBox { public ComboBoxEx() { this.DrawMode = DrawMode.OwnerDrawFixed; this.DrawItem += ComboBoxEx_DrawItem; this.DropDownBorderColor = Color.Red; this.DropDownBackColor = Color.Yellow; } [Category("Appearance")] [Description("The border color of the drop down list")] [DefaultValue(typeof(Color), "Red")] public Color DropDownBorderColor { get; set; } [Category("Appearance")] [Description("The background color of the drop down list")] [DefaultValue(typeof(Color), "Yellow")] public Color DropDownBackColor { get; set; } void ComboBoxEx_DrawItem(object sender, DrawItemEventArgs e) { if (e.Index < 0) return; if ((e.State & DrawItemState.ComboBoxEdit) == DrawItemState.ComboBoxEdit) return // Draw the background of the item. if ( ((e.State & DrawItemState.Focus) == DrawItemState.Focus) || ((e.State & DrawItemState.Selected) == DrawItemState.Selected) || ((e.State & DrawItemState.HotLight) == DrawItemState.HotLight) ) { e.DrawBackground(); } else { Brush backgroundBrush = new SolidBrush(DropDownBackColor); e.Graphics.FillRectangle(backgroundBrush, e.Bounds); } //Draw item text e.Graphics.DrawString(Items[e.Index].ToString(), this.Font, Brushes.Black, new RectangleF(e.Bounds.X, e.Bounds.Y, e.Bounds.Width, e.Bounds.Height)); // Draw the focus rectangle if the mouse hovers over an item. if ((e.State & DrawItemState.Focus) == DrawItemState.Focus) e.DrawFocusRectangle(); //Draw the border around the whole DropDown area Pen borderPen = new Pen(DropDownBorderColor, 1); Point start; Point end; if (e.Index == 0) { //Draw top border start = new Point(e.Bounds.Left, e.Bounds.Top); end = new Point(e.Bounds.Left + e.Bounds.Width - 1, e.Bounds.Top); e.Graphics.DrawLine(borderPen, start, end); } //Draw left border start = new Point(e.Bounds.Left, e.Bounds.Top); end = new Point(e.Bounds.Left, e.Bounds.Top + e.Bounds.Height - 1); e.Graphics.DrawLine(borderPen, start, end); //Draw Right border start = new Point(e.Bounds.Left + e.Bounds.Width - 1, e.Bounds.Top); end = new Point(e.Bounds.Left + e.Bounds.Width - 1, e.Bounds.Top + e.Bounds.Height - 1); e.Graphics.DrawLine(borderPen, start, end); if (e.Index == Items.Count - 1) { //Draw bottom border start = new Point(e.Bounds.Left, e.Bounds.Top + e.Bounds.Height - 1); end = new Point(e.Bounds.Left + e.Bounds.Width - 1, e.Bounds.Top + e.Bounds.Height - 1); e.Graphics.DrawLine(borderPen, start, end); } } }
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原文地址:http://www.cnblogs.com/rinack/p/4442244.html