TextBox class
https://docs.microsoft.com/zh-cn/dotnet/api/system.windows.forms.textbox?view=netframework-4.8
When using the TextBox control, the user can enter text in the application. This control has other features not found in standard Windows text box controls, including multiline editing and password character masking.
Generally, the TextBox control is used to display or accept a line of text as input. You can use the " Multiline " and " ScrollBars " properties to enable display or enter multiple lines of text. Set the AcceptsTab and AcceptsReturn properties to enable larger text operations truein multi-line TextBox controls.
You can limit the amount of text entered in the TextBox control by setting the MaxLength property to a specific number of characters . The TextBox control can also be used to accept passwords and other sensitive information. You can use the PasswordChar property to mask characters entered in the single-line version of the control. Using the " CharacterCasing " attribute allows the user to type only uppercase, lowercase, or a combination of uppercase and lowercase characters with the TextBox control.
To scroll the content of the TextBox until the cursor (caret) is in the visible area of the control, you can use the ScrollToCaret method. To select the range of text in the text box, you can use the Select method.
To limit text input in the TextBox control, you can create an event handler for the KeyDown event to verify each character entered in the control. You can also limit all data input in the TextBox control by setting the ReadOnly property trueto .
Attributes
| AcceptsReturn | Gets or sets a value indicating whether a new line of text is created in the control or the form's default button is activated when the Enter key is pressed in a multiline TextBox control. |
| AcceptsTab | Gets or sets a value indicating whether to press a Tab character in the control when pressing the Tab key in a multiline text box control, instead of moving the focus to the next control in the order of the tabs. (Inherited from TextBoxBase ) |
| AllowDrop | Gets or sets a value indicating whether the control can accept data that the user drags and drops onto it. (Inherited from Control ) |
| AutoSize | Gets or sets a value indicating whether the height of the control is automatically adjusted when the font assigned to the control is changed. (Inherited from TextBoxBase ) |
| BackColor | Gets or sets the background color of the control. (Inherited from TextBoxBase ) |
| CanUndo | Gets a value indicating whether the user can undo the previous operation in the text box control. (Inherited from TextBoxBase ) |
| ForeColor | Gets or sets the foreground color of the control. (Inherited from TextBoxBase ) |
| Lines | Gets or sets the text line in the text box control. (Inherited from TextBoxBase ) |
| Location | Gets or sets the coordinates of the upper-left corner of the control relative to the upper-left corner of its container. (Inherited from Control ) |
| MaxLength | Gets or sets the maximum number of characters that users can type or paste in the text box control. (Inherited from TextBoxBase ) |
| Multiline | Gets or sets a value indicating whether this is a multi-line TextBox control. |
| ReadOnly | Gets or sets a value indicating whether the text in the text box is read-only. (Inherited from TextBoxBase ) |
| ScrollBars | Gets or sets which scroll bars should appear in the multi-line TextBox control. |
| SelectedText | Gets or sets a value indicating the currently selected text in the control. (Inherited from TextBoxBase ) |
| SelectionStart | Gets or sets the starting point of the selected text in the text box. (Inherited from TextBoxBase ) |
| Text | Gets or sets the text associated with this control. |
| textAlign | |
| TextLength | Get the length of the text in the control. (Inherited from TextBoxBase ) |
method
| AppendText(String) | Append text to the current text in the text box. (Inherited from TextBoxBase ) |
| Clear() | Clear all text from the text box control. (Inherited from TextBoxBase ) |
| Copy() | 将文本框中的当前选定内容复制到“剪贴板”。 (继承自 TextBoxBase) |
| CreateGraphics() | 为控件创建 Graphics。 (继承自 Control) |
| Cut() | 将文本框中的当前选定内容移动到“剪贴板”中。 (继承自 TextBoxBase) |
| DeselectAll() | 将 SelectionLength 属性的值指定为零，从而不会在控件中选择字符。 (继承自 TextBoxBase) |
| DoDragDrop(Object, DragDropEffects) | 开始拖放操作。 (继承自 Control) |
| Paste() | 用剪贴板的内容替换文本框中的当前选定内容。 (继承自 TextBoxBase) |
| Paste(String) | 将选定文本设置为指定文本，但不清除撤消缓冲区。 |
| Select() | 激活控件。 (继承自 Control) |
| Undo() | 撤消文本框中的上一个编辑操作。 (继承自 TextBoxBase) |
| Update() | 使控件重绘其工作区内的无效区域。 (继承自 Control) |
对话框类Form是定义在 Windows名称空间下的类,对话框类中定义了一个名为Controls的属性,用于表示对话框上的所有控件。 Controls为控件集合,可利用下标访问每个控件。集合变量的使用方法类似于数组,可通过下标指定访问的集合元素。
本例控件及其属性值
| 控件 | 属性 | 值 | 控件 | 属性 | 值 |
| TextBox | Name | txtText | Button | Name | btnClear |
| Multiline | true | text | 清除 | ||
| text | Button | Name | btnReadOnly | ||
| Button | Name | btnCopy | Text | 只读 | |
| Text | 复制 | Button | Name | btnUndo | |
| Button | Name | btnCut | Text | 撤消 | |
| Text | 剪切 | Button | Name | btnPaste | |
| Text | 粘贴 |
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
txtText.Width = Me.Width
txtText.Height = 220
txtText.Left = 0
txtText.Top = 0
txtText.WordWrap = True '是否自动换行
End Sub
Private Sub btnCopy_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCopy.Click
Static tempStr As String
tempStr = txtText.SelectedText
If tempStr = "" Then
MsgBox("选择文本")
End If
String.Copy(tempStr)
End Sub
Private Sub btnPaste_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPaste.Click
txtText.Paste()
End Sub
Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
txtText.Clear()
End Sub
Private Sub btnUndo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnUndo.Click
txtText.Undo()
End Sub
Private Sub btnReadOnly_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnReadOnly.Click
Dim i As Integer
If txtText.ReadOnly Then
btnReadOnly.Text = "只读"
txtText.ReadOnly = False
For i = 0 To Me.Controls.Count - 1
Me.Controls(i).Enabled = True
Next
Else
btnReadOnly.Text = "可写"
txtText.ReadOnly = True
For i = 0 To Me.Controls.Count - 1
If Not (Me.Controls(i) Is btnReadOnly) Then
Me.Controls(i).Enabled = False
End If
Next
End If
End Sub
Private Sub btnCut_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCut.Click
txtText.Cut()
End Sub
End Class
