WatermarkComboBox 和 WatermarkTextBox

直接给出代码

一、WatermarkComboBox（转）

/* 作者：Starts_2000
* 日期：2009-07-25
* 网站：http://www.csharpwin.com CS 程序员之窗。
* 你可以免费使用或修改以下代码，但请保留版权信息。
* 具体请查看 CS程序员之窗开源协议（http://www.csharpwin.com/csol.html）。
*/

Code Snippet

1. namespace CSharpWin
2. {
3.     /* ×÷??￡oStarts_2000
4.      * è?期ú￡o2009-07-25
5.      * í?站?￡ohttp://www.csharpwin.com CS 3ìDò员±之?′°。￡
6.      * 你?可éò?免a·?ê1ó?或òDT改?ò?下?′ú码?￡?μ???±￡á?°?è¨D?息￠。￡
7.      * 具?ì???2é看′ CS3ìDò员±之?′°开a源′D-òé￡¨http://www.csharpwin.com/csol.html￡?。￡
8.      */
9.  
10.     [ToolboxBitmap(typeof(ComboBox))]
11.     public class WatermarkComboBox : ComboBox
12.     {
13.         private string _emptyTextTip;
14.         private Color _emptyTextTipColor = Color.DarkGray;
15.         private IntPtr _editHandle;
16.         private EditNativeWindow _editNativeWindow;
17.  
18.         public WatermarkComboBox()
19.             : base()
20.         {
21.         }
22.  
23.         [DefaultValue("")]
24.         public string EmptyTextTip
25.         {
26.             get { return _emptyTextTip; }
27.             set
28.             {
29.                 _emptyTextTip = value;
30.                 base.Invalidate();
31.             }
32.         }
33.  
34.         [DefaultValue(typeof(Color), "DarkGray")]
35.         public Color EmptyTextTipColor
36.         {
37.             get { return _emptyTextTipColor; }
38.             set
39.             {
40.                 _emptyTextTipColor = value;
41.                 base.Invalidate();
42.             }
43.         }
44.  
45.         internal IntPtr EditHandle
46.         {
47.             get { return _editHandle; }
48.         }
49.  
50.         internal Rectangle EditRect
51.         {
52.             get
53.             {
54.                 if (DropDownStyle != ComboBoxStyle.DropDownList)
55.                 {
56.                     if (IsHandleCreated && EditHandle != IntPtr.Zero)
57.                     {
58.                         RECT rcClient = new RECT();
59.                         GetWindowRect(EditHandle, ref rcClient);
60.                         return RectangleToClient(rcClient.Rect);
61.                     }
62.                 }
63.                 return Rectangle.Empty;
64.             }
65.         }
66.  
67.         [DllImport("user32.dll")]
68.         private static extern bool GetComboBoxInfo(
69.             IntPtr hwndCombo, ref ComboBoxInfo info);
70.  
71.         [DllImport("user32.dll")]
72.         private static extern int GetWindowRect(IntPtr hwnd, ref RECT lpRect);
73.  
74.         [StructLayout(LayoutKind.Sequential)]
75.         public struct RECT
76.         {
77.             public int Left;
78.             public int Top;
79.             public int Right;
80.             public int Bottom;
81.  
82.             public RECT(int left, int top, int right, int bottom)
83.             {
84.                 Left = left;
85.                 Top = top;
86.                 Right = right;
87.                 Bottom = bottom;
88.             }
89.  
90.             public RECT(Rectangle rect)
91.             {
92.                 Left = rect.Left;
93.                 Top = rect.Top;
94.                 Right = rect.Right;
95.                 Bottom = rect.Bottom;
96.             }
97.  
98.             public Rectangle Rect
99.             {
100.                 get
101.                 {
102.                     return new Rectangle(
103.                         Left,
104.                         Top,
105.                         Right - Left,
106.                         Bottom - Top);
107.                 }
108.             }
109.  
110.             public Size Size
111.             {
112.                 get
113.                 {
114.                     return new Size(Right - Left, Bottom - Top);
115.                 }
116.             }
117.  
118.             public static RECT FromXYWH(int x, int y, int width, int height)
119.             {
120.                 return new RECT(x,
121.                                 y,
122.                                 x + width,
123.                                 y + height);
124.             }
125.  
126.             public static RECT FromRectangle(Rectangle rect)
127.             {
128.                 return new RECT(rect.Left,
129.                                  rect.Top,
130.                                  rect.Right,
131.                                  rect.Bottom);
132.             }
133.         }
134.  
135.         private struct ComboBoxInfo
136.         {
137.             public int cbSize;
138.             public RECT rcItem;
139.             public RECT rcButton;
140.             public ComboBoxButtonState stateButton;
141.             public IntPtr hwndCombo;
142.             public IntPtr hwndEdit;
143.             public IntPtr hwndList;
144.         }
145.  
146.         private enum ComboBoxButtonState
147.         {
148.             STATE_SYSTEM_NONE = 0,
149.             STATE_SYSTEM_INVISIBLE = 0x00008000,
150.             STATE_SYSTEM_PRESSED = 0x00000008
151.         }
152.  
153.         protected override void OnHandleCreated(EventArgs e)
154.         {
155.             base.OnHandleCreated(e);
156.             ComboBoxInfo cbi = new ComboBoxInfo();
157.             cbi.cbSize = Marshal.SizeOf(cbi);
158.             GetComboBoxInfo(base.Handle, ref cbi);
159.             _editHandle = cbi.hwndEdit;
160.             if (DropDownStyle != ComboBoxStyle.DropDownList)
161.             {
162.                 _editNativeWindow = new EditNativeWindow(this);
163.             }
164.         }
165.  
166.         protected override void OnHandleDestroyed(EventArgs e)
167.         {
168.             base.OnHandleDestroyed(e);
169.             if (_editNativeWindow != null)
170.             {
171.                 _editNativeWindow.Dispose();
172.                 _editNativeWindow = null;
173.             }
174.         }
175.  
176.         private class EditNativeWindow : NativeWindow, IDisposable
177.         {
178.             private WatermarkComboBox _owner;
179.             private const int WM_PAINT = 0xF;
180.  
181.             public EditNativeWindow(WatermarkComboBox owner)
182.                 : base()
183.             {
184.                 _owner = owner;
185.                 AssignHandle(_owner.EditHandle);
186.             }
187.  
188.             [DllImport("user32.dll")]
189.             private static extern IntPtr GetDC(IntPtr ptr);
190.  
191.             [DllImport("user32.dll")]
192.             private static extern int ReleaseDC(IntPtr hwnd, IntPtr hDC);
193.  
194.             protected override void WndProc(ref Message m)
195.             {
196.                 base.WndProc(ref m);
197.                 if (m.Msg == WM_PAINT)
198.                 {
199.                     IntPtr handle = m.HWnd;
200.                     IntPtr hdc = GetDC(handle);
201.                     if (hdc == IntPtr.Zero)
202.                     {
203.                         return;
204.                     }
205.                     try
206.                     {
207.                         using (Graphics graphics = Graphics.FromHdc(hdc))
208.                         {
209.                             if (_owner.Text.Length == 0
210.                                 && !_owner.Focused
211.                                 && !string.IsNullOrEmpty(_owner.EmptyTextTip))
212.                             {
213.                                 TextFormatFlags format =
214.                                     TextFormatFlags.EndEllipsis |
215.                                     TextFormatFlags.VerticalCenter;
216.  
217.                                 if (_owner.RightToLeft == RightToLeft.Yes)
218.                                 {
219.                                     format |= TextFormatFlags.RightToLeft | TextFormatFlags.Right;
220.                                 }
221.  
222.                                 TextRenderer.DrawText(
223.                                     graphics,
224.                                     _owner.EmptyTextTip,
225.                                     _owner.Font,
226.                                     new Rectangle(0, 0, _owner.EditRect.Width, _owner.EditRect.Height),
227.                                     _owner.EmptyTextTipColor,
228.                                     format);
229.                             }
230.                         }
231.                     }
232.                     finally
233.                     {
234.                         ReleaseDC(handle, hdc);
235.                     }
236.                 }
237.             }
238.  
239.             #region IDisposable 3é员±
240.  
241.             public void Dispose()
242.             {
243.                 ReleaseHandle();
244.                 _owner = null;
245.             }
246.  
247.             #endregion
248.         }
249.     }
250. }

二、WatermarkTextBox（转）

Code Snippet

1. namespace CSharpWin
2. {
3.       /* 作??Starts_2000
4.        * 日期?2009-07-25
5.        * 网站?http://www.csharpwin.com CS 程序员之窗。
6.        * 你可以免?使用或修改以下代码?但?保留版权信息。
7.        * 具体?查看 CS程序员之窗开源协??http://www.csharpwin.com/csol.html?。
8.        */
9.  
10.     [ToolboxBitmap(typeof(TextBox))]
11.     public class WatermarkTextBox : TextBox
12.     {
13.         private string _emptyTextTip;
14.         private Color _emptyTextTipColor = Color.DarkGray;
15.  
16.         private const int WM_PAINT = 0xF;
17.  
18.         public WatermarkTextBox()
19.             : base()
20.         {
21.         }
22.  
23.         [DefaultValue("")]
24.         public string EmptyTextTip
25.         {
26.             get { return _emptyTextTip; }
27.             set
28.             {
29.                 _emptyTextTip = value;
30.                 base.Invalidate();
31.             }
32.         }
33.  
34.         [DefaultValue(typeof(Color), "DarkGray")]
35.         public Color EmptyTextTipColor
36.         {
37.             get { return _emptyTextTipColor; }
38.             set
39.             {
40.                 _emptyTextTipColor = value;
41.                 base.Invalidate();
42.             }
43.         }
44.  
45.         protected override void WndProc(ref Message m)
46.         {
47.             base.WndProc(ref m);
48.             if (m.Msg == WM_PAINT)
49.             {
50.                 WmPaint(ref m);
51.             }
52.         }
53.  
54.         private void WmPaint(ref Message m)
55.         {
56.             using (Graphics graphics = Graphics.FromHwnd(base.Handle))
57.             {
58.                 if (Text.Length == 0
59.                     && !string.IsNullOrEmpty(_emptyTextTip)
60.                     && !Focused)
61.                 {
62.                     TextFormatFlags format =
63.                         TextFormatFlags.EndEllipsis |
64.                         TextFormatFlags.VerticalCenter;
65.  
66.                     if (RightToLeft == RightToLeft.Yes)
67.                     {
68.                         format |= TextFormatFlags.RightToLeft | TextFormatFlags.Right;
69.                     }
70.  
71.                     TextRenderer.DrawText(
72.                         graphics,
73.                         _emptyTextTip,
74.                         Font,
75.                         base.ClientRectangle,
76.                         _emptyTextTipColor,
77.                         format);
78.                 }
79.             }
80.         }
81.     }
82. }