本文共 7176 字，大约阅读时间需要 23 分钟。
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。
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Install-Package HZH_Controls
GDI+画图，不了解先百度
思路:
控件扩展属性，在组件中对需要显示倒影的控件的父控件添加Paint事件，在Paint事件中绘制控件，并旋转180，然后画到父控件上，然后再覆盖一层渐变色，完美。
添加一个类ShadowComponent继承Component，实现IExtenderProvider接口，扩展属性
代码比较少，直接放上来了
1 /// 2 /// The m control cache 3 /// 4 Dictionary m_controlCache = new Dictionary(); 5 6 #region 构造函数 English:Constructor 7 /// 8 /// Initializes a new instance of the class. 9 /// 10 public ShadowComponent() 11 { 12 13 } 14 15 /// 16 /// Initializes a new instance of the class. 17 /// 18 /// The container. 19 public ShadowComponent(IContainer container) 20 : this() 21 { 22 container.Add(this); 23 } 24 #endregion 25 26 /// 27 /// 指定此对象是否可以将其扩展程序属性提供给指定的对象。 28 /// 29 /// 要接收扩展程序属性的 。 30 /// 如果此对象可以扩展程序属性提供给指定对象，则为 true；否则为 false。 31 public bool CanExtend(object extendee) 32 { 33 if (extendee is Control && !(extendee is Form)) 34 return true; 35 return false; 36 } 37 38 /// 39 /// Gets the show shadow. 40 /// 41 /// The control. 42 /// true if XXXX, false otherwise. 43 [Browsable(true), Category("自定义属性"), Description("是否显示倒影"), 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 /// 53 /// Sets the show shadow. 54 /// 55 /// The control. 56 /// if set to true [is show shadow]. 57 public void SetShowShadow(Control control, bool isShowShadow) 58 { 59 control.ParentChanged += control_ParentChanged; 60 m_controlCache[control] = isShowShadow; 61 } 62 63 /// 64 /// Handles the ParentChanged event of the control control. 65 /// 66 /// The source of the event. 67 /// The instance containing the event data. 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 /// 85 /// The LST paint event control 86 /// 87 List lstPaintEventControl = new List(); 88 /// 89 /// The shadow height 90 /// 91 private float shadowHeight = 0.3f; 92 93 /// 94 /// Gets or sets the height of the shadow. 95 /// 96 /// The height of the shadow. 97 [Browsable(true), Category("自定义属性"), Description("倒影高度，0-1"), Localizable(true)] 98 public float ShadowHeight 99 {100 get { return shadowHeight; }101 set { shadowHeight = value; }102 } 103 /// 104 /// The BLN loading105 /// 106 bool blnLoading = false;107 /// 108 /// Handles the Paint event of the Parent control.109 /// 110 /// The source of the event.111 /// The instance containing the event data.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 /// 151 /// Gets the color of the parent.152 /// 153 /// The c.154 /// Color. 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 }
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