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

麻烦博客下方点个【推荐】，谢谢

NuGet

Install-Package HZH_Controls

Ŀ¼

https://www.cnblogs.com/bfyx/p/11364884.html

用处及效果

此效果只是牛刀小试，需要注意的是，像textbox这样的控件并不起作用，请注意。

你可以向目标控件绘图，画任何你想画的东西

准备工作

没什么可准备的

开始

添加一个类GraphicalOverlay ，继承Component

代码比较少，一次全上了，主要就是用控件的paint事件搞事情，逻辑比较简单

  1 using System;   2 using System.ComponentModel;   3 using System.Drawing;   4 using System.Windows.Forms;   5    6 namespace HZH_Controls.Controls   7 {   8     [DefaultEvent("Paint")]   9     public partial class GraphicalOverlay : Component  10     {  11         public event EventHandler<PaintEventArgs> Paint;  12           13         public GraphicalOverlay()  14         {  15             InitializeComponent();  16         }  17   18         public GraphicalOverlay(IContainer container)  19         {  20             container.Add(this);  21   22             InitializeComponent();  23         }  24         private Control owner;        25         public Control Owner  26         {  27             get { return owner; }  28             set  29             {  30                 // The owner form cannot be set to null.  31                 if (value == null)  32                     throw new ArgumentNullException();  33   34                 // The owner form can only be set once.  35                 if (owner != null)  36                     throw new InvalidOperationException();  37   38                 // Save the form for future reference.  39                 owner = value;  40   41                 // Handle the form's Resize event.  42                 owner.Resize += new EventHandler(Form_Resize);  43   44                 // Handle the Paint event for each of the controls in the form's hierarchy.  45                 ConnectPaintEventHandlers(owner);  46             }  47         }  48   49         private void Form_Resize(object sender, EventArgs e)  50         {  51             owner.Invalidate(true);  52         }  53   54         private void ConnectPaintEventHandlers(Control control)  55         {  56             // Connect the paint event handler for this control.  57             // Remove the existing handler first (if one exists) and replace it.  58             control.Paint -= new PaintEventHandler(Control_Paint);  59             control.Paint += new PaintEventHandler(Control_Paint);  60   61             control.ControlAdded -= new ControlEventHandler(Control_ControlAdded);  62             control.ControlAdded += new ControlEventHandler(Control_ControlAdded);  63   64             // Recurse the hierarchy.  65             foreach (Control child in control.Controls)  66                 ConnectPaintEventHandlers(child);  67         }  68   69         private void Control_ControlAdded(object sender, ControlEventArgs e)  70         {  71             // Connect the paint event handler for the new control.  72             ConnectPaintEventHandlers(e.Control);  73         }  74   75         private void Control_Paint(object sender, PaintEventArgs e)  76         {  77             // As each control on the form is repainted, this handler is called.  78   79             Control control = sender as Control;  80             Point location;  81   82             // Determine the location of the control's client area relative to the form's client area.  83             if (control == owner)  84                 // The form's client area is already form-relative.  85                 location = control.Location;  86             else  87             {  88                 // The control may be in a hierarchy, so convert to screen coordinates and then back to form coordinates.  89                 location = owner.PointToClient(control.Parent.PointToScreen(control.Location));  90   91                 // If the control has a border shift the location of the control's client area.  92                 location += new Size((control.Width - control.ClientSize.Width) / 2, (control.Height - control.ClientSize.Height) / 2);  93             }  94   95             // Translate the location so that we can use form-relative coordinates to draw on the control.  96             if (control != owner)  97                 e.Graphics.TranslateTransform(-location.X, -location.Y);  98   99             // Fire a paint event. 100             OnPaint(sender, e); 101         } 102  103         private void OnPaint(object sender, PaintEventArgs e) 104         { 105             // Fire a paint event. 106             // The paint event will be handled in Form1.graphicalOverlay1_Paint(). 107  108             if (Paint != null) 109                 Paint(sender, e); 110         } 111     } 112 } 113  114 namespace System.Windows.Forms 115 { 116     using System.Drawing; 117  118     public static class Extensions 119     { 120         public static Rectangle Coordinates(this Control control) 121         { 122             // Extend System.Windows.Forms.Control to have a Coordinates property. 123             // The Coordinates property contains the control's form-relative location. 124             Rectangle coordinates; 125             Form form = (Form)control.TopLevelControl; 126  127             if (control == form) 128                 coordinates = form.ClientRectangle; 129             else 130                 coordinates = form.RectangleToClient(control.Parent.RectangleToScreen(control.Bounds)); 131  132             return coordinates; 133         } 134     } 135 }