前提

入行已經7,8年了，一直想做一套漂亮點的自定義控制元件，於是就有了本系列文章。

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

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

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NuGet

Install-Package HZH_Controls

目錄

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

用處及效果

準備工作

GDI+畫圖，不瞭解先百度

開始

思路：

控制元件擴充套件屬性，在元件中對需要顯示倒影的控制元件的父控制元件新增Paint事件，在Paint事件中繪製控制元件，並旋轉180，然後畫到父控制元件上，然後再覆蓋一層漸變色，完美。

新增一個類ShadowComponent 繼承Component，實現 IExtenderProvider介面，擴充套件屬性

程式碼比較少，直接放上來了

  1 /// <summary>
  2         /// The m control cache
  3         /// </summary>
  4         Dictionary<Control, bool> m_controlCache = new Dictionary<Control, bool>();
  5 
  6         #region 建構函式    English:Constructor
  7         /// <summary>
  8         /// Initializes a new instance of the <see cref="ShadowComponent" /> class.
  9         /// </summary>
 10         public ShadowComponent()
 11         {
 12 
 13         }
 14 
 15         /// <summary>
 16         /// Initializes a new instance of the <see cref="ShadowComponent" /> class.
 17         /// </summary>
 18         /// <param name="container">The container.</param>
 19         public ShadowComponent(IContainer container)
 20             : this()
 21         {
 22             container.Add(this);
 23         }
 24         #endregion
 25 
 26         /// <summary>
 27         /// 指定此物件是否可以將其擴充套件程式屬性提供給指定的物件。
 28         /// </summary>
 29         /// <param name="extendee">要接收擴充套件程式屬性的 <see cref="T:System.Object" />。</param>
 30         /// <returns>如果此物件可以擴充套件程式屬性提供給指定物件，則為 true；否則為 false。</returns>
 31         public bool CanExtend(object extendee)
 32         {
 33             if (extendee is Control && !(extendee is Form))
 34                 return true;
 35             return false;
 36         }
 37 
 38         /// <summary>
 39         /// Gets the show shadow.
 40         /// </summary>
 41         /// <param name="control">The control.</param>
 42         /// <returns><c>true</c> if XXXX, <c>false</c> otherwise.</returns>
 43         [Browsable(true), Category("自定義屬性"), Description("是否顯示倒影"), DisplayName("ShowShadow"), Localizable(true)]
 44         public bool GetShowShadow(Control control)
 45         {
 46             if (m_controlCache.ContainsKey(control))
 47                 return m_controlCache[control];
 48             else
 49                 return false;
 50         }
 51 
 52         /// <summary>
 53         /// Sets the show shadow.
 54         /// </summary>
 55         /// <param name="control">The control.</param>
 56         /// <param name="isShowShadow">if set to <c>true</c> [is show shadow].</param>
 57         public void SetShowShadow(Control control, bool isShowShadow)
 58         {
 59             control.ParentChanged += control_ParentChanged;
 60             m_controlCache[control] = isShowShadow;
 61         }
 62 
 63         /// <summary>
 64         /// Handles the ParentChanged event of the control control.
 65         /// </summary>
 66         /// <param name="sender">The source of the event.</param>
 67         /// <param name="e">The <see cref="EventArgs"/> instance containing the event data.</param>
 68         void control_ParentChanged(object sender, EventArgs e)
 69         {
 70             Control control = sender as Control;
 71             if (control.Parent != null && m_controlCache[control])
 72             {
 73                 if (!lstPaintEventControl.Contains(control.Parent))
 74                 {
 75                     lstPaintEventControl.Add(control.Parent);
 76                     Type type = control.Parent.GetType();
 77                     System.Reflection.PropertyInfo pi = type.GetProperty("DoubleBuffered", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
 78                     pi.SetValue(control.Parent, true, null);
 79                     control.Parent.Paint += Parent_Paint;
 80                 }
 81             }
 82         }
 83 
 84         /// <summary>
 85         /// The LST paint event control
 86         /// </summary>
 87         List<Control> lstPaintEventControl = new List<Control>();
 88         /// <summary>
 89         /// The shadow height
 90         /// </summary>
 91         private float shadowHeight = 0.3f;
 92 
 93         /// <summary>
 94         /// Gets or sets the height of the shadow.
 95         /// </summary>
 96         /// <value>The height of the shadow.</value>
 97         [Browsable(true), Category("自定義屬性"), Description("倒影高度，0-1"), Localizable(true)]
 98         public float ShadowHeight
 99         {
100             get { return shadowHeight; }
101             set { shadowHeight = value; }
102         }
103         /// <summary>
104         /// The BLN loading
105         /// </summary>
106         bool blnLoading = false;
107         /// <summary>
108         /// Handles the Paint event of the Parent control.
109         /// </summary>
110         /// <param name="sender">The source of the event.</param>
111         /// <param name="e">The <see cref="PaintEventArgs"/> instance containing the event data.</param>
112         void Parent_Paint(object sender, PaintEventArgs e)
113         {
114             if (blnLoading)
115                 return;           
116             if (shadowHeight > 0)
117             {
118                 var control = sender as Control;
119                 var lst = m_controlCache.Where(p => p.Key.Parent == control && p.Value);
120                 if (lst != null && lst.Count() > 0)
121                 {
122                     blnLoading = true;
123                     e.Graphics.SetGDIHigh();
124                     foreach (var item in lst)
125                     {
126                         Control _control = item.Key;
127 
128                         using (Bitmap bit = new Bitmap(_control.Width, _control.Height))
129                         {
130                             _control.DrawToBitmap(bit, _control.ClientRectangle);
131                             using (Bitmap bitNew = new Bitmap(bit.Width, (int)(bit.Height * shadowHeight)))
132                             {
133                                 using (var g = Graphics.FromImage(bitNew))
134                                 {
135                                     g.DrawImage(bit, new RectangleF(0, 0, bitNew.Width, bitNew.Height), new RectangleF(0, bit.Height - bit.Height * shadowHeight, bit.Width, bit.Height * shadowHeight), GraphicsUnit.Pixel);
136                                 }
137                                 bitNew.RotateFlip(RotateFlipType.Rotate180FlipNone);
138                                 e.Graphics.DrawImage(bitNew, new Point(_control.Location.X, _control.Location.Y + _control.Height + 1));
139                                 Color bgColor = GetParentColor(_control);
140                                 LinearGradientBrush lgb = new LinearGradientBrush(new Rectangle(_control.Location.X, _control.Location.Y + _control.Height + 1, bitNew.Width, bitNew.Height), Color.FromArgb(50, bgColor), bgColor, 90f);   //75f 表示角度
141                                 e.Graphics.FillRectangle(lgb, new Rectangle(new Point(_control.Location.X, _control.Location.Y + _control.Height + 1), bitNew.Size));
142                             }
143                         }
144                     }
145                 }
146             }
147             blnLoading = false;
148         }
149 
150         /// <summary>
151         /// Gets the color of the parent.
152         /// </summary>
153         /// <param name="c">The c.</param>
154         /// <returns>Color.</returns>
155         private Color GetParentColor(Control c)
156         {
157             if (c.Parent.BackColor != Color.Transparent)
158             {
159                 return c.Parent.BackColor;
160             }
161             return GetParentColor(c.Parent);
162         }

最後的話

如果你喜歡的話，請到 https://gitee.com/kwwwvagaa/net_winform_custom_control 點個星