自定义组合框，GDI+中出现一般错误

本文关键字：错误 组合 GDI+ 自定义 | 更新日期: 2023-09-27 18:21:58

我的BorderedComboBox中出现了一个问题"GDI+中发生了一个通用错误"，它只出现在最终项目中（在新的WinForm应用程序中可以）。我想这是关于IntPtr未被管理和处置不当的问题，但我需要一些帮助来解决。

错误代码停止在：

ControlPaint.DrawBorder(gdc, rectBorder, _BorderColor, ButtonBorderStyle.Solid);

提前感谢

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
/* Simplified version of Eugenis, BorderedComboBox
 */
namespace mySpace
{
    public partial class BorderedComboBox : ComboBox
    {

        public BorderedComboBox()
            : base()
        {
            hDC = GetDC(Handle);
            gdc = Graphics.FromHdc(hDC);
            rectBorder = new Rectangle(0, 0, Width, Height);
            SetStyle(ControlStyles.DoubleBuffer, true);
            SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
            SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            SetStyle(ControlStyles.UserPaint, false);
        }
        private const int WM_ERASEBKGND = 0x14;
        private const int WM_PAINT = 0xF;
        private const int WM_NC_PAINT = 0x85;
        private const int WM_PRINTCLIENT = 0x318;
        private const int WM_MOUSEHOVER = 0x2A1;
        private const int WM_MOUSELEAVE = 0x2A3;
        private IntPtr hDC;
        private Graphics gdc;
        private Rectangle rectBorder;
        private Color _BorderColor = SystemColors.Window;
        [Category("BorderFocusStyle")]
        [Description("User-defined border color.")]
        public Color BorderColor
        {
            get
            {
                return _BorderColor;
            }
            set
            {
                _BorderColor = value;
                this.Refresh();
            }
        }

        protected override void WndProc(ref Message m)
        {
            if (this.DropDownStyle == ComboBoxStyle.Simple)
            {
                base.WndProc(ref m);
                return;
            }
            switch (m.Msg)
            {
                case WM_NC_PAINT:
                    break;
                case WM_PAINT:
                    base.WndProc(ref m);
                    ControlPaint.DrawBorder(gdc, rectBorder, _BorderColor, ButtonBorderStyle.Solid);
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }

        [DllImport("user32")]
        private static extern IntPtr GetDC(IntPtr hWnd);
        [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = CharSet.Auto)]
        extern static bool DestroyIcon(IntPtr hWnd);
    }
}

自定义组合框，GDI+中出现一般错误

OnPaint（）建议工作不好，背景难看等。然而，这是一个工作版本，以备任何人需要。不确定是否释放和销毁非托管IntPtr。谢谢你的建议。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
/* A color bordered combobox 
 */
namespace yo3hcv
{
    public partial class BorderedComboBox : ComboBox
    {
        public BorderedComboBox()
            : base()
        {
            SetStyle(ControlStyles.DoubleBuffer, true);
            SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
            SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            SetStyle(ControlStyles.UserPaint, false);

        }
        private const int WM_SIZE = 0x0005;
        private const int WM_SIZING = 0x0214;
        private const int WM_ERASEBKGND = 0x14;
        private const int WM_PAINT = 0xF;
        private const int WM_NC_PAINT = 0x85;
        private const int WM_PRINTCLIENT = 0x318;
        private const int WM_MOUSEHOVER = 0x2A1;
        private const int WM_MOUSELEAVE = 0x2A3;

        private Color _BorderColor = SystemColors.Window;
        //private Color _BorderColor = Color.Red;
        [Category("BorderFocusStyle")]
        [Description("User-defined border color.")]
        public Color BorderColor
        {
            get
            {
                return _BorderColor;
            }
            set
            {
                _BorderColor = value;
                Invalidate();
            }
        }

        protected override void OnGotFocus(System.EventArgs e)
        {
            Invalidate();
            base.OnGotFocus(e);
        }
        protected override void OnLostFocus(System.EventArgs e)
        {
            Invalidate();
            base.OnLostFocus(e);
        }
        protected override void OnResize(EventArgs e)
        {
            Invalidate();
            base.OnResize(e);
        }
        protected override void OnSelectedValueChanged(EventArgs e)
        {
            Invalidate();
            base.OnSelectedValueChanged(e);
        }
        protected override void WndProc(ref Message m)
        {
            IntPtr hDC;
            Graphics gdc;
            if (this.DropDownStyle == ComboBoxStyle.Simple)
            {
                base.WndProc(ref m);
                return;
            }
            switch (m.Msg)
            {
                case WM_NC_PAINT:
                    break;
                case WM_PAINT:
                    base.WndProc(ref m);
                    hDC = GetDC(this.Handle);
                    gdc = Graphics.FromHdc(hDC);

                    Rectangle rect = new Rectangle(0, 0, this.Width, this.Height);
                    ControlPaint.DrawBorder(gdc, rect, _BorderColor, ButtonBorderStyle.Solid);
                    ReleaseDC(m.HWnd, hDC);
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }

        [DllImport("user32.dll")]
        static extern Int32 ReleaseDC(IntPtr hwnd, IntPtr hdc);
        [DllImport("user32")]
        private static extern IntPtr GetDC(IntPtr hWnd);

    }
}
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