（七十五）c#Winform自定义控件-控件水印组件

官网

http://www.hzhcontrols.com

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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麻烦博客下方点个【推荐】，谢谢

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，此效果只是向控件覆盖一个半透明随机颜色

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

 using System;
 using System.ComponentModel;
 using System.Drawing;
 using System.Windows.Forms;

 namespace HZH_Controls.Controls
 {
     [DefaultEvent("Paint")]
     public partial class GraphicalOverlay : Component
     {
         public event EventHandler<PaintEventArgs> Paint;

         public GraphicalOverlay()
         {
             InitializeComponent();
         }

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

             InitializeComponent();
         }
         private Control owner;
         public Control Owner
         {
             get { return owner; }
             set
             {
                 // The owner form cannot be set to null.
                 if (value == null)
                     throw new ArgumentNullException();

                 // The owner form can only be set once.
                 if (owner != null)
                     throw new InvalidOperationException();

                 // Save the form for future reference.
                 owner = value;

                 // Handle the form's Resize event.
                 owner.Resize += new EventHandler(Form_Resize);

                 // Handle the Paint event for each of the controls in the form's hierarchy.
                 ConnectPaintEventHandlers(owner);
             }
         }

         private void Form_Resize(object sender, EventArgs e)
         {
             owner.Invalidate(true);
         }

         private void ConnectPaintEventHandlers(Control control)
         {
             // Connect the paint event handler for this control.
             // Remove the existing handler first (if one exists) and replace it.
             control.Paint -= new PaintEventHandler(Control_Paint);
             control.Paint += new PaintEventHandler(Control_Paint);

             control.ControlAdded -= new ControlEventHandler(Control_ControlAdded);
             control.ControlAdded += new ControlEventHandler(Control_ControlAdded);

             // Recurse the hierarchy.
             foreach (Control child in control.Controls)
                 ConnectPaintEventHandlers(child);
         }

         private void Control_ControlAdded(object sender, ControlEventArgs e)
         {
             // Connect the paint event handler for the new control.
             ConnectPaintEventHandlers(e.Control);
         }

         private void Control_Paint(object sender, PaintEventArgs e)
         {
             // As each control on the form is repainted, this handler is called.

             Control control = sender as Control;
             Point location;

             // Determine the location of the control's client area relative to the form's client area.
             if (control == owner)
                 // The form's client area is already form-relative.
                 location = control.Location;
             else
             {
                 // The control may be in a hierarchy, so convert to screen coordinates and then back to form coordinates.
                 location = owner.PointToClient(control.Parent.PointToScreen(control.Location));

                 // If the control has a border shift the location of the control's client area.
                 location += new Size((control.Width - control.ClientSize.Width) / , (control.Height - control.ClientSize.Height) / );
             }

             // Translate the location so that we can use form-relative coordinates to draw on the control.
             if (control != owner)
                 e.Graphics.TranslateTransform(-location.X, -location.Y);

             // Fire a paint event.
             OnPaint(sender, e);
         }

         private void OnPaint(object sender, PaintEventArgs e)
         {
             // Fire a paint event.
             // The paint event will be handled in Form1.graphicalOverlay1_Paint().

             if (Paint != null)
                 Paint(sender, e);
         }
     }
 }

 namespace System.Windows.Forms
 {
     using System.Drawing;

     public static class Extensions
     {
         public static Rectangle Coordinates(this Control control)
         {
             // Extend System.Windows.Forms.Control to have a Coordinates property.
             // The Coordinates property contains the control's form-relative location.
             Rectangle coordinates;
             Form form = (Form)control.TopLevelControl;

             if (control == form)
                 coordinates = form.ClientRectangle;
             else
                 coordinates = form.RectangleToClient(control.Parent.RectangleToScreen(control.Bounds));

             return coordinates;
         }
     }
 }

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