项目中遇到需要下拉框列表内容为线类型或点类型图形的需求，想到可以使用手绘线条和图形的方式来实现下拉列表内容自定义，记录下来供大家参考学习之用。

在项目中添加一个组件

添加完之后会显示如下设计界面

这里直接点击切换到代码视图即可

注意：新建的组件默认继承Component，我们这里是要自定义一个ComboBox下拉框，所以要继承自ComboBox，此类位于using System.Windows.Forms命名空间下

线的类型列表

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

namespace CustomComponents
{
    /// <summary>
    /// 填充线型
    /// </summary>
    public partial class FillLineTypeCbo : ComboBox
    {
        public FillLineTypeCbo()
        {
      		//初始化组件
            InitializeComponent();
        }

        public FillLineTypeCbo(IContainer container)
        {
            container.Add(this);

            InitializeComponent();
            InitItems();
        }

        private void InitItems()
        {
            this.DrawMode = DrawMode.OwnerDrawFixed;//手动绘制所有元素
            this.DropDownStyle = ComboBoxStyle.DropDownList;//下拉框样式设置为不能编辑
            this.Items.Clear();//清空原有项 
        }

        public enum LineType
        {
            DoubleHorizontalLine = 0,//双横线
            VerticalLine,//垂直线
            LeftSlash,//左斜线
            RightSlash,//右斜线
            VerticalGridlines,//垂直网格线
            CrossGridlines,//交叉网格线
            SolidBrush,//实心刷
            HollowBrush,//空心刷
        }
        //protected
        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            if (e.Index >= 0)//判断是否需要重绘
            {
                int typeId = int.Parse(this.Items[e.Index].ToString());//获取选项id

                Font font = new Font("宋体", 9);//定义字体
                Rectangle rect = e.Bounds;
                //rect.Inflate(-2, -2);//缩放一定大小
                rect.Inflate(5, -2);//缩放一定大小
                Pen pen = null;
                SolidBrush solidBrush = new SolidBrush(Color.Black);

                float offSet = rect.Height / 2;
                float x = rect.Width / 10;
                float y = rect.Top + offSet;//如果设置成e.ItemHeigh*e.Index +offSet,则在选中节点后，由于Item位置固定，因此Item不能显示出来。
                switch (typeId)
                {
                    case (int)LineType.DoubleHorizontalLine:
                        pen = new Pen(Color.Black, 1);
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(8 * x, y));//绘制水平线
                        e.Graphics.DrawLine(pen, new PointF(x, y + 5), new PointF(8 * x, y + 5));
                        //e.Graphics.DrawLine(pen, new PointF(x, y+2), new PointF(x, y+2));
                        break;
                    case (int)LineType.VerticalLine:
                        pen = new Pen(Color.Black, 1);
                        //绘制垂直线
                        int xNum = 0;
                        for (int i = 0; i < 10; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNum, y - 4), new PointF(1 * x + xNum, y + 6));
                            xNum += 7;

                        }
                        break;
                    case (int)LineType.LeftSlash:
                        pen = new Pen(Color.Black, 1);
                        //绘制左斜线
                        int xNumLeftSlash = 0;
                        for (int i = 0; i < 10; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNumLeftSlash, y - 4), new PointF(x + 5 + xNumLeftSlash, y + 7));
                            xNumLeftSlash += 7;
                        }
                        break;
                    case (int)LineType.RightSlash:
                        pen = new Pen(Color.Black, 1);
                        //绘制右斜线
                        int xNumRightSlash = 0;
                        for (int i = 0; i < 10; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNumRightSlash + 7, y - 4), new PointF(x + xNumRightSlash, y + 7));
                            xNumRightSlash += 7;
                        }
                        break;
                    case (int)LineType.VerticalGridlines:
                        pen = new Pen(Color.Black, 1);
                        //绘制垂直网格线
                        xNum = 0;
                        for (int i = 0; i < 10; i++)//绘制竖线
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNum, y - 4), new PointF(1 * x + xNum, y + 6));
                            xNum += 7;
                        }
                        //绘制双横线
                        e.Graphics.DrawLine(pen, new PointF(x - 3, y - 2), new PointF(8 * x, y - 2));
                        e.Graphics.DrawLine(pen, new PointF(x - 3, y + 5), new PointF(8 * x, y + 5));
                        break;
                    case (int)LineType.CrossGridlines:
                        pen = new Pen(Color.Black, 1);
                        //绘制交叉网格线
                        //绘制左斜线
                        xNumLeftSlash = 0;
                        for (int i = 0; i < 10; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNumLeftSlash, y - 4), new PointF(x + 10 + xNumLeftSlash, y + 7));
                            xNumLeftSlash += 7;
                        }
                        //绘制右斜线
                        xNumRightSlash = 0;
                        for (int i = 0; i < 10; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNumRightSlash + 10, y - 4), new PointF(x + xNumRightSlash, y + 7));
                            xNumRightSlash += 7;
                        }
                        break;
                    case (int)LineType.SolidBrush:
                        pen = new Pen(Color.Black, 10);
                        //绘制实心刷
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(8 * x, y));
                        break;
                    case (int)LineType.HollowBrush:
                        pen = new Pen(Color.Black, 1);
                        //绘制空心刷
                        e.Graphics.DrawLine(pen, new PointF(x, y - 6), new PointF(x, y + 6));//左
                        e.Graphics.DrawLine(pen, new PointF(x, y - 6), new PointF(8 * x, y - 6));//上
                        e.Graphics.DrawLine(pen, new PointF(8 * x, y - 6), new PointF(8 * x, y + 6));//右
                        e.Graphics.DrawLine(pen, new PointF(x, y + 6), new PointF(8 * x, y + 6));//下
                        break;
                    default:
                        pen = new Pen(Color.Black, 1);
                        break;
                }
            }
        }
    }
}

边框线类型列表

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

namespace CustomComponents
{
    /// <summary>
    /// 线型
    /// </summary>
    public partial class LineShapeCbo : ComboBox
    {
        public LineShapeCbo()
        {
            InitializeComponent();
        }

        public LineShapeCbo(IContainer container)
        {
            container.Add(this);

            InitializeComponent();
            InitItems();
        }

        private void InitItems()
        {
            this.DrawMode = DrawMode.OwnerDrawFixed;//手动绘制所有元素
            this.DropDownStyle = ComboBoxStyle.DropDownList;//下拉框样式设置为不能编辑
            this.Items.Clear();//清空原有项 
        }

        public enum LineType
        {
            SolidLine = 0,//实线
            LongDisconnection,//长间断线
            ShortEndLine,//短间端线
            LongAndShort,//长短相间
            ShortToLong,//长短短相间
            EmptyBrushes//空画笔
        }

        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            if (e.Index >= 0)//判断是否需要重绘
            {
                int typeId = int.Parse(this.Items[e.Index].ToString());//获取选项id

                Font font = new Font("宋体", 9);//定义字体
                Rectangle rect = e.Bounds;
                //rect.Inflate(-2, -2);//缩放一定大小
                rect.Inflate(5, -2);//缩放一定大小
                Pen pen = null;
                SolidBrush solidBrush = new SolidBrush(Color.Black);

                float offSet = rect.Height / 2;
                float x = rect.Width / 10;
                float y = rect.Top + offSet;//如果设置成e.ItemHeigh*e.Index +offSet,则在选中节点后，由于Item位置固定，因此Item不能显示出来。
                switch (typeId)
                {
                    case (int)LineType.SolidLine:
                        pen = new Pen(Color.Black, 1);
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(8 * x, y));//绘制实线
                        //e.Graphics.DrawLine(pen, new PointF(x, y+2), new PointF(x, y+2));
                        break;
                    case (int)LineType.LongDisconnection:
                        pen = new Pen(Color.Black, 1);
                        //绘制长间断线
                        int xNum = 0;
                        for (int i = 0; i < 3; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNum, y), new PointF(15+x + xNum, y));
                            xNum += 20;
                        }
                        e.Graphics.DrawLine(pen, new PointF(x + xNum, y), new PointF(10 + x + xNum, y));
                        break;
                    case (int)LineType.ShortEndLine:
                        pen = new Pen(Color.Black, 1);
                        //绘制短间端线
                        xNum = 0;
                        for (int i = 0; i < 8; i++)
                        {
                            e.Graphics.DrawLine(pen, new PointF(x + xNum, y), new PointF(6 + x + xNum, y));
                            xNum += 9;
                        }
                        break;
                    case (int)LineType.LongAndShort:
                        pen = new Pen(Color.Black, 1);
                        //绘制长短相间
                            e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(x+10, y));
                            e.Graphics.DrawLine(pen, new PointF(x+15, y), new PointF(x+20, y));
                            e.Graphics.DrawLine(pen, new PointF(x+25, y), new PointF(x+35, y));
                            e.Graphics.DrawLine(pen, new PointF(x+40, y), new PointF(x+45, y));
                            e.Graphics.DrawLine(pen, new PointF(x+50, y), new PointF(x+60, y));
                            e.Graphics.DrawLine(pen, new PointF(x+65, y), new PointF(x+70, y));
                        break;
                    case (int)LineType.ShortToLong:
                        pen = new Pen(Color.Black, 1);
                        //绘制长短短相间
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(x + 10, y));
                        e.Graphics.DrawLine(pen, new PointF(x+15, y), new PointF(x + 18, y));
                        e.Graphics.DrawLine(pen, new PointF(x+23, y), new PointF(x + 26, y));
                        e.Graphics.DrawLine(pen, new PointF(x+31, y), new PointF(x + 41, y));
                        e.Graphics.DrawLine(pen, new PointF(x + 46, y), new PointF(x + 49, y));
                        e.Graphics.DrawLine(pen, new PointF(x + 54, y), new PointF(x + 57, y));
                        e.Graphics.DrawLine(pen, new PointF(x + 62, y), new PointF(x + 70, y));
                        break;
                    case (int)LineType.EmptyBrushes:
                        pen = new Pen(Color.Black, 1);
                        //绘制空画笔
                        break;
                    //case (int)LineType.LineWithPoints:
                    default:
                        pen = new Pen(Color.Black, 1);
                        break;
                }
                //if (e.Index < 9)
                //{
                //    e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(8 * x, y));//绘制线
                //    //Rectangle rectColor = new Rectangle(rect.Location, new Size(9 * (int)x, rect.Height));
                //    //e.Graphics.DrawRectangle(Pens.Black, rectColor);//绘制边框
                //}
            }
        }
    }
}

点类型列表

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace CustomComponents
{
    /// <summary>
    /// 点类型
    /// </summary>
    public partial class PointTypeCbo : ComboBox
    {
        public PointTypeCbo()
        {
            InitializeComponent();
        }

        public PointTypeCbo(IContainer container)
        {
            container.Add(this);

            InitializeComponent();
            InitItems();
        }
        private void InitItems()
        {
            this.DrawMode = DrawMode.OwnerDrawFixed;//手动绘制所有元素
            this.DropDownStyle = ComboBoxStyle.DropDownList;//下拉框样式设置为不能编辑
            this.Items.Clear();//清空原有项 
        }

        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            if (e.Index >= 0)//判断是否需要重绘
            {
                int typeId = int.Parse(this.Items[e.Index].ToString());//获取选项id

                Font font = new Font("宋体", 9);//定义字体
                Rectangle rect = e.Bounds;
                //rect.Inflate(-2, -2);//缩放一定大小
                rect.Inflate(5, -2);//缩放一定大小
                Pen pen = null;
                SolidBrush solidBrush = new SolidBrush(Color.Black);

                float offSet = rect.Height / 2;
                float x = rect.Width / 10;
                float y = rect.Top + offSet;//如果设置成e.ItemHeigh*e.Index +offSet,则在选中节点后，由于Item位置固定，因此Item不能显示出来。
                switch (typeId)
                {
                    case 0:
                        pen = new Pen(Color.Red, 1);//设置边框
                        //SolidBrush sb0 = new SolidBrush(Color.Black);//设置填充颜色
                        //绘制
                        //e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(8 * x, y));
                        //Graphics g = CreateGraphics();
                        //Brush myBrush = new SolidBrush(Color.Green);
                        //string str = "just for fun";
                        //Font myFont = new Font("宋体", 9, FontStyle.Bold);
                        //e.Graphics.DrawString(str, myFont, myBrush, 60, 20);          
                        //e.Graphics.FillEllipse(sb0, 10 ,10 , 10, 10);
                        e.Graphics.DrawEllipse(pen, 9, 5, 10, 10);
                        break;
                    case 1:
                        pen = new Pen(Color.Red, 1);
                        //绘制正方形
                        e.Graphics.DrawLine(pen, new PointF(x, y - 5), new PointF(x, y + 5));//左
                        e.Graphics.DrawLine(pen, new PointF(x, y - 5), new PointF(x + 10, y - 5));//上
                        e.Graphics.DrawLine(pen, new PointF(x + 10, y - 5), new PointF(x + 10, y + 5));//右
                        e.Graphics.DrawLine(pen, new PointF(x, y + 5), new PointF(x + 10, y + 5));//下

                        //Rectangle rectColor = new Rectangle(rect.Location, new Size(10, 10));
                        //e.Graphics.DrawRectangle(Pens.Black, rectColor);//绘制边框

                        break;
                    case 2:
                        pen = new Pen(Color.Red, 1);
                        //绘制十字形
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(x + 10, y));//横
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y - 5), new PointF(x + 5, y + 5));//竖
                        break;
                    case 3:
                        pen = new Pen(Color.Red, 1);
                        //绘制三角形
                        e.Graphics.DrawLine(pen, new PointF(x, y + 5), new PointF(x + 5, y - 5));//左
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y - 5), new PointF(x + 10, y + 5));//右
                        e.Graphics.DrawLine(pen, new PointF(x, y + 5), new PointF(x + 10, y + 5));//下
                        break;
                    case 4:
                        pen = new Pen(Color.Red, 1);
                        //绘制右（三角）红旗
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y + 5), new PointF(x + 5, y - 5));//竖杆
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y - 5), new PointF(x + 10, y));//红旗右边
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y), new PointF(x + 10, y));//红旗下边
                        break;
                    case 5:
                        pen = new Pen(Color.Red, 1);
                        //绘制左（三角）红旗 
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y + 5), new PointF(x + 5, y - 5));//竖杆
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(x + 5, y - 5));//红旗左边
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(x + 5, y));//红旗下边
                        break;
                    case 6:
                        pen = new Pen(Color.Red, 1);
                        //绘制右方旗
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y + 5), new PointF(x + 5, y - 5));//竖杆
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y - 5), new PointF(x + 10, y - 5));//右上边
                        e.Graphics.DrawLine(pen, new PointF(x + 10, y - 5), new PointF(x + 10, y));//右右边
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y), new PointF(x + 10, y));//右下边
                        break;
                    case 7:
                        pen = new Pen(Color.Red, 1);
                        //绘制大圆包小圆
                        //e.Graphics.DrawEllipse(pen, 20, 115, 10, 10);//空心大圆
                        //e.Graphics.DrawEllipse(pen, 13, 118, 4, 4);//空心小圆 
                        e.Graphics.DrawEllipse(pen, x, y - 5, 10, 10);//空心大圆
                        e.Graphics.DrawEllipse(pen, x + 3, y - 5 + 3, 4, 4);//空心小圆
                        //Rectangle rectColor = new Rectangle(rect.Location, new Size(9 * (int)x, rect.Height));
                        //e.Graphics.DrawRectangle(Pens.Black, rectColor);//绘制边框
                        break;
                    case 8:
                        pen = new Pen(Color.Red, 1);
                        //绘制大圆加十字
                        e.Graphics.DrawEllipse(pen, x, y - 5, 10, 10);//空心大圆
                        //绘制十字形
                        e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(x + 10, y));//横
                        e.Graphics.DrawLine(pen, new PointF(x + 5, y - 5), new PointF(x + 5, y + 5));//竖
                        break;
                    case 9:
                        pen = new Pen(Color.Red, 1);
                        //绘制实心圆
                        SolidBrush sb9 = new SolidBrush(Color.Green);//设置填充颜色
                        e.Graphics.DrawEllipse(pen, x, y - 5, 10, 10);//实心圆边框
                        e.Graphics.FillEllipse(sb9, x, y - 5, 10, 10);//实心圆填充
                        break;
                    case 10:
                        pen = new Pen(Color.Red, 1);
                        //绘制实心正方形
                        //绘制正方形
                        e.Graphics.DrawRectangle(pen, x, y - 5, 10, 10);
                        SolidBrush sb10 = new SolidBrush(Color.Green);//设置填充颜色
                        e.Graphics.FillRectangle(sb10, x, y - 5, 10, 10);
                        break;
                    case 11:
                        pen = new Pen(Color.Red, 1);
                        //绘制
                        PointF p1 = new PointF(x + 5, y - 5);
                        PointF p2 = new PointF(x, y + 5);
                        PointF p3 = new PointF(x + 10, y + 5);
                        PointF[] points = new PointF[3];
                        Brush myBrush = new SolidBrush(Color.Green);
                        points[0] = p1;
                        points[1] = p2;
                        points[2] = p3;
                        e.Graphics.FillPolygon(myBrush, points, FillMode.Alternate);
                        e.Graphics.DrawPolygon(pen, points);
                        break;
                    //case (int)LineType.LineWithPoints:
                    default:
                        pen = new Pen(Color.Black, 1);
                        break;
                }
                if (e.Index < 12)
                {
                    //e.Graphics.DrawLine(pen, new PointF(x, y), new PointF(8 * x, y));//绘制线
                    //设置后面的字符串
                    Rectangle Rect = new Rectangle(rect.Location, new Size(5 * (int)x, rect.Height));

                    //文本内容显示区域
                    Rectangle textRect =
                            new Rectangle(Rect.Right + 2, Rect.Y, e.Bounds.Width - Rect.Width, e.Bounds.Height - 2);

                    //文本格式垂直居中
                    StringFormat strFormat = new StringFormat();
                    strFormat.LineAlignment = StringAlignment.Center;
                    e.Graphics.DrawString((e.Index + 1).ToString(), new Font("微软雅黑", 12), Brushes.Black, textRect, strFormat);
                }
            }
        }
    }
}

带图片的列表

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace ShowState
{
    /// <summary>
    /// 下拉框  下拉列表 图片显示
    /// </summary>
    public partial class ComboBoxImg : ComboBox
    {
        public ComboBoxImg()
        {
            InitializeComponent();
            DrawMode = DrawMode.OwnerDrawFixed;
            DropDownStyle = ComboBoxStyle.DropDownList;
            ItemHeight = 50;
            Width = 40;
        }

        public ComboBoxImg(IContainer container)
        {
            container.Add(this);
            InitializeComponent();

            DrawMode = DrawMode.OwnerDrawFixed;
            DropDownStyle = ComboBoxStyle.DropDownList;
            ItemHeight = 200;
            Width = 40;
        }

        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            if (Items.Count == 0 || e.Index == -1)
                return;
            if ((e.State & DrawItemState.Selected) != 0)
            {
                //渐变画刷
                LinearGradientBrush brush = new LinearGradientBrush(e.Bounds, Color.FromArgb(255, 251, 237),
                                                 Color.FromArgb(255, 236, 181), LinearGradientMode.Vertical);
                //填充区域
                Rectangle borderRect = new Rectangle(3, e.Bounds.Y, e.Bounds.Width - 5, e.Bounds.Height - 2);

                e.Graphics.FillRectangle(brush, borderRect);

                //画边框
                Pen pen = new Pen(Color.FromArgb(229, 195, 101));
                e.Graphics.DrawRectangle(pen, borderRect);
            }
            else
            {
                SolidBrush brush = new SolidBrush(Color.FromArgb(255, 255, 255));
                e.Graphics.FillRectangle(brush, e.Bounds);
            }

            //获得项图片,绘制图片
            ItemEx item = (ItemEx)Items[e.Index];
            Image img = item.Image;

            //图片绘制的区域
            Rectangle imgRect = new Rectangle(6, e.Bounds.Y + 3, 45, 45);
            e.Graphics.DrawImage(img, imgRect);

            //文本内容显示区域
            Rectangle textRect =
                    new Rectangle(imgRect.Right + 2, imgRect.Y, e.Bounds.Width - imgRect.Width, e.Bounds.Height - 2);

            //获得项文本内容,绘制文本
            String itemText = Items[e.Index].ToString();

            //文本格式垂直居中
            StringFormat strFormat = new StringFormat();
            strFormat.LineAlignment = StringAlignment.Center;
            e.Graphics.DrawString(itemText, new Font("微软雅黑", 12), Brushes.Black, textRect, strFormat);
            base.OnDrawItem(e);
        }

    }

    /// <summary>
    /// 下拉框  下拉列表 图片显示
    /// </summary>
    public class ItemEx
    {
        /// <summary>
        /// 图片显示
        /// </summary>
        /// <param name="text">文本</param>
        /// <param name="img">图片（图片路径）</param>
        public ItemEx(string text, Image img)
        {
            Text = text;
            Image = img;
        }

        public string Text { get; set; }
        public Image Image { get; set; }

        public override string ToString()
        {
            return Text;
        }
    }
}

组件编写完之后，进入工具箱，就能看到当前项目中我们自定义的组件了，使用方法跟普通控件方法完全相同，直接拖到窗体即可

如何将下拉框设为阻止用户输入——只能选择无法输入

1.将DropDownStyle的属性设为DropDownList

2.使用代码实时修改

			//设置样式为用户无法输入
            _selebox_1.DropDownStyle = ComboBoxStyle.DropDownList;
            //设置样式为用户可以输入
            _selebox_1.DropDownStyle = ComboBoxStyle.DropDown;
            //设置样式为简单组合框-暂没有测试过
            _selebox_1.DropDownStyle = ComboBoxStyle.Simple;

如何设置Combox下拉框控件的初始选择项

       public Window()
        {
            InitializeComponent();
            //0代表第一个值，在初始化窗口后选择第一个值
            _selebox_1.SelectedIndex = 0;
        }

在代码中获取Combox下拉框控件选择的值

		public void test()
        {
            //获取下拉框当前选择的值，并转换为string
            string result = _selebox_1.SelectedItem.ToString();
        }

在代码中给Combox下拉框控件添加删除值

        public void test()
        {
            //给下拉框添加一个值
            _selebox_1.Items.Add("添加一个选项");
            //把下拉框指定的值删除
            _selebox_1.Items.Remove("添加一个选项");
            //或者用索引删除指定的值,0代表第一项
            _selebox_1.Items.RemoveAt(0);
        }

前提

入行已经7,8年了，一直想做一套漂亮点的自定义控件，于是就有了本系列文章。

GitHub：https://github.com/kwwwvagaa/NetWinformControl

码云：https://gitee.com/kwwwvagaa/net_winform_custom_control.git

如果觉得写的还行，请点个 star 支持一下吧

欢迎前来交流探讨： 企鹅群568015492 

麻烦博客下方点个【推荐】，谢谢

NuGet

Install-Package HZH_Controls

目录

https://blog.csdn.net/kwwwvagaa/article/details/100586547

用处及效果

准备工作

这个控件将继承自（三）c#Winform自定义控件-有图标的按钮，如不了解，请移步查看

开始

添加一个用户控件UCDropDownBtn，继承自UCBtnImg

处理一些属性

 1 Forms.FrmAnchor _frmAnchor;
 2         private int _dropPanelHeight = -1;
 3         public new event EventHandler BtnClick;
 4         [Description("下拉框高度"), Category("自定义")]
 5         public int DropPanelHeight
 6         {
 7             get { return _dropPanelHeight; }
 8             set { _dropPanelHeight = value; }
 9         }
10         private string[] btns ;
11         [Description("按钮"), Category("自定义")]
12         public string[] Btns
13         {
14             get { return btns; }
15             set { btns = value; }
16         }
17         [Obsolete("不再可用的属性")]
18         [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
19         public override Image Image
20         {
21             get;
22             set;
23         }
24         [Obsolete("不再可用的属性")]
25         [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
26         public override ContentAlignment ImageAlign
27         {
28             get;
29             set;
30         }

点击时候显示下拉框

 1 void UCDropDownBtn_BtnClick(object sender, EventArgs e)
 2         {
 3             if (_frmAnchor == null || _frmAnchor.IsDisposed || _frmAnchor.Visible == false)
 4             {
 5 
 6                 if (Btns != null && Btns.Length > 0)
 7                 {
 8                     int intRow = 0;
 9                     int intCom = 1;
10                     var p = this.PointToScreen(this.Location);
11                     while (true)
12                     {
13                         int intScreenHeight = Screen.PrimaryScreen.Bounds.Height;
14                         if ((p.Y + this.Height + Btns.Length / intCom * 50 < intScreenHeight || p.Y - Btns.Length / intCom * 50 > 0)
15                             && (_dropPanelHeight <= 0 ? true : (Btns.Length / intCom * 50 <= _dropPanelHeight)))
16                         {
17                             intRow = Btns.Length / intCom + (Btns.Length % intCom != 0 ? 1 : 0);
18                             break;
19                         }
20                         intCom++;
21                     }
22                     UCTimePanel ucTime = new UCTimePanel();
23                     ucTime.IsShowBorder = true;
24                     int intWidth = this.Width / intCom;
25 
26                     Size size = new Size(intCom * intWidth, intRow * 50);
27                     ucTime.Size = size;
28                     ucTime.FirstEvent = true;
29                     ucTime.SelectSourceEvent += ucTime_SelectSourceEvent;
30                     ucTime.Row = intRow;
31                     ucTime.Column = intCom;
32 
33                     List<KeyValuePair<string, string>> lst = new List<KeyValuePair<string, string>>();
34                     foreach (var item in Btns)
35                     {
36                         lst.Add(new KeyValuePair<string, string>(item, item));
37                     }
38                     ucTime.Source = lst;
39 
40                     _frmAnchor = new Forms.FrmAnchor(this, ucTime);
41                     _frmAnchor.Load += (a, b) => { (a as Form).Size = size; };
42 
43                     _frmAnchor.Show(this.FindForm());
44 
45                 }
46             }
47             else
48             {
49                 _frmAnchor.Close();
50             }
51         }

处理一下按钮事件

 1 void ucTime_SelectSourceEvent(object sender, EventArgs e)
 2         {
 3             if (_frmAnchor != null && !_frmAnchor.IsDisposed && _frmAnchor.Visible)
 4             {
 5                 _frmAnchor.Close();
 6 
 7                 if (BtnClick != null)
 8                 {
 9                     BtnClick(sender.ToString(), e);
10                 }
11             }
12         }

完整代码

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;

namespace HZH_Controls.Controls.Btn
{
    [DefaultEvent("BtnClick")]
    public partial class UCDropDownBtn : UCBtnImg
    {
        Forms.FrmAnchor _frmAnchor;
        private int _dropPanelHeight = -1;
        public new event EventHandler BtnClick;
        [Description("下拉框高度"), Category("自定义")]
        public int DropPanelHeight
        {
            get { return _dropPanelHeight; }
            set { _dropPanelHeight = value; }
        }
        private string[] btns ;
        [Description("按钮"), Category("自定义")]
        public string[] Btns
        {
            get { return btns; }
            set { btns = value; }
        }
        [Obsolete("不再可用的属性")]
        [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
        public override Image Image
        {
            get;
            set;
        }
        [Obsolete("不再可用的属性")]
        [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
        public override ContentAlignment ImageAlign
        {
            get;
            set;
        }

        public UCDropDownBtn()
        {
            InitializeComponent();
            IsShowTips = false;
            this.lbl.Image=Properties.Resources.ComboBox;
            this.lbl.ImageAlign = ContentAlignment.MiddleRight;
            base.BtnClick += UCDropDownBtn_BtnClick;
        }

        void UCDropDownBtn_BtnClick(object sender, EventArgs e)
        {
            if (_frmAnchor == null || _frmAnchor.IsDisposed || _frmAnchor.Visible == false)
            {

                if (Btns != null && Btns.Length > 0)
                {
                    int intRow = 0;
                    int intCom = 1;
                    var p = this.PointToScreen(this.Location);
                    while (true)
                    {
                        int intScreenHeight = Screen.PrimaryScreen.Bounds.Height;
                        if ((p.Y + this.Height + Btns.Length / intCom * 50 < intScreenHeight || p.Y - Btns.Length / intCom * 50 > 0)
                            && (_dropPanelHeight <= 0 ? true : (Btns.Length / intCom * 50 <= _dropPanelHeight)))
                        {
                            intRow = Btns.Length / intCom + (Btns.Length % intCom != 0 ? 1 : 0);
                            break;
                        }
                        intCom++;
                    }
                    UCTimePanel ucTime = new UCTimePanel();
                    ucTime.IsShowBorder = true;
                    int intWidth = this.Width / intCom;

                    Size size = new Size(intCom * intWidth, intRow * 50);
                    ucTime.Size = size;
                    ucTime.FirstEvent = true;
                    ucTime.SelectSourceEvent += ucTime_SelectSourceEvent;
                    ucTime.Row = intRow;
                    ucTime.Column = intCom;

                    List<KeyValuePair<string, string>> lst = new List<KeyValuePair<string, string>>();
                    foreach (var item in Btns)
                    {
                        lst.Add(new KeyValuePair<string, string>(item, item));
                    }
                    ucTime.Source = lst;

                    _frmAnchor = new Forms.FrmAnchor(this, ucTime);
                    _frmAnchor.Load += (a, b) => { (a as Form).Size = size; };

                    _frmAnchor.Show(this.FindForm());

                }
            }
            else
            {
                _frmAnchor.Close();
            }
        }
        void ucTime_SelectSourceEvent(object sender, EventArgs e)
        {
            if (_frmAnchor != null && !_frmAnchor.IsDisposed && _frmAnchor.Visible)
            {
                _frmAnchor.Close();

                if (BtnClick != null)
                {
                    BtnClick(sender.ToString(), e);
                }
            }
        }
    }
}

namespace HZH_Controls.Controls.Btn
{
    partial class UCDropDownBtn
    {
        /// <summary> 
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary> 
        /// 清理所有正在使用的资源。
        /// </summary>
        /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region 组件设计器生成的代码

        /// <summary> 
        /// 设计器支持所需的方法 - 不要
        /// 使用代码编辑器修改此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {
            System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(UCDropDownBtn));
            this.SuspendLayout();
            // 
            // lbl
            // 
            this.lbl.Font = new System.Drawing.Font("微软雅黑", 14F);
            this.lbl.ForeColor = System.Drawing.Color.White;
            this.lbl.ImageAlign = System.Drawing.ContentAlignment.MiddleRight;
            this.lbl.ImageList = null;
            this.lbl.Text = "自定义按钮";
            this.lbl.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
            // 
            // UCDropDownBtn
            // 
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
            this.BtnFont = new System.Drawing.Font("微软雅黑", 14F);
            this.BtnForeColor = System.Drawing.Color.White;
            this.ForeColor = System.Drawing.Color.White;
            this.Image = ((System.Drawing.Image)(resources.GetObject("$this.Image")));
            this.ImageAlign = System.Drawing.ContentAlignment.MiddleRight;
            this.Margin = new System.Windows.Forms.Padding(2);
            this.Name = "UCDropDownBtn";
            this.ResumeLayout(false);

        }

        #endregion
    }
}

最后的话

如果你喜欢的话，请到 https://gitee.com/kwwwvagaa/net_winform_custom_control 点个星星吧