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

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NuGet

Install-Package HZH_Controls

目录

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.Forms115 {116 using System.Drawing;117 118 public static class Extensions119  {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 else130 coordinates = form.RectangleToClient(control.Parent.RectangleToScreen(control.Bounds));131 132 return coordinates;133  }134  }135 }

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