TextBoxBase.SelectionStart 属性

定义

获取或设置文本框中选定的文本起始点。Gets or sets the starting point of text selected in the text box.

public:
 property int SelectionStart { int get(); void set(int value); };
[System.ComponentModel.Browsable(false)]
public int SelectionStart { get; set; }
member this.SelectionStart : int with get, set
Public Property SelectionStart As Integer

属性值

文本框中选定的文本的起始位置。The starting position of text selected in the text box.

属性

异常

赋给的值小于零。The assigned value is less than zero.

示例

示例1Example 1

下面的代码示例使用TextBox派生类。The following code example uses TextBox, a derived class. 它为Click MenuItem执行剪切、复制、粘贴和撤消操作的对象提供事件处理程序。It provides Click event handlers for MenuItem objects that perform Cut, Copy, Paste, and Undo operations. 此示例需要创建名TextBoxtextBox1的控件。This example requires that a TextBox control named textBox1 has been created.

private:
   void Menu_Copy( System::Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Ensure that text is selected in the text box.   
      if ( textBox1->SelectionLength > 0 )
      {
         // Copy the selected text to the Clipboard.
         textBox1->Copy();
      }
   }

   void Menu_Cut( System::Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Ensure that text is currently selected in the text box.   
      if (  !textBox1->SelectedText->Equals( "" ) )
      {
         // Cut the selected text in the control and paste it into the Clipboard.
         textBox1->Cut();
      }
   }

   void Menu_Paste( System::Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Determine if there is any text in the Clipboard to paste into the text box.
      if ( Clipboard::GetDataObject()->GetDataPresent( DataFormats::Text ) == true )
      {
         // Determine if any text is selected in the text box.
         if ( textBox1->SelectionLength > 0 )
         {
            // Ask user if they want to paste over currently selected text.
            if ( MessageBox::Show( "Do you want to paste over current selection?",
               "Cut Example", MessageBoxButtons::YesNo ) == ::DialogResult::No )
            {
               // Move selection to the point after the current selection and paste.
               textBox1->SelectionStart = textBox1->SelectionStart + textBox1->SelectionLength;
            }
         }
         // Paste current text in Clipboard into text box.
         textBox1->Paste();
      }
   }

   void Menu_Undo( System::Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Determine if last operation can be undone in text box.   
      if ( textBox1->CanUndo == true )
      {
         // Undo the last operation.
         textBox1->Undo();
         // Clear the undo buffer to prevent last action from being redone.
         textBox1->ClearUndo();
      }
   }
private void Menu_Copy(System.Object sender, System.EventArgs e)
 {
    // Ensure that text is selected in the text box.   
    if(textBox1.SelectionLength > 0)
        // Copy the selected text to the Clipboard.
        textBox1.Copy();
 }
 
 private void Menu_Cut(System.Object sender, System.EventArgs e)
 {   
     // Ensure that text is currently selected in the text box.   
     if(textBox1.SelectedText != "")
        // Cut the selected text in the control and paste it into the Clipboard.
        textBox1.Cut();
 }
 
 private void Menu_Paste(System.Object sender, System.EventArgs e)
 {
    // Determine if there is any text in the Clipboard to paste into the text box.
    if(Clipboard.GetDataObject().GetDataPresent(DataFormats.Text) == true)
    {
        // Determine if any text is selected in the text box.
        if(textBox1.SelectionLength > 0)
        {
          // Ask user if they want to paste over currently selected text.
          if(MessageBox.Show("Do you want to paste over current selection?", "Cut Example", MessageBoxButtons.YesNo) == DialogResult.No)
             // Move selection to the point after the current selection and paste.
             textBox1.SelectionStart = textBox1.SelectionStart + textBox1.SelectionLength;
        }
        // Paste current text in Clipboard into text box.
        textBox1.Paste();
    }
 }
 
 
 private void Menu_Undo(System.Object sender, System.EventArgs e)
 {
    // Determine if last operation can be undone in text box.   
    if(textBox1.CanUndo == true)
    {
       // Undo the last operation.
       textBox1.Undo();
       // Clear the undo buffer to prevent last action from being redone.
       textBox1.ClearUndo();
    }
 }
 
Private Sub Menu_Copy(sender As System.Object, e As System.EventArgs)
    ' Ensure that text is selected in the text box.   
    If textBox1.SelectionLength > 0 Then
        ' Copy the selected text to the Clipboard.
        textBox1.Copy()
    End If
End Sub
 
Private Sub Menu_Cut(sender As System.Object, e As System.EventArgs)
    ' Ensure that text is currently selected in the text box.   
    If textBox1.SelectedText <> "" Then
        ' Cut the selected text in the control and paste it into the Clipboard.
        textBox1.Cut()
    End If
End Sub
 
Private Sub Menu_Paste(sender As System.Object, e As System.EventArgs)
    ' Determine if there is any text in the Clipboard to paste into the text box.
    If Clipboard.GetDataObject().GetDataPresent(DataFormats.Text) = True Then
        ' Determine if any text is selected in the text box.
        If textBox1.SelectionLength > 0 Then
            ' Ask user if they want to paste over currently selected text.
            If MessageBox.Show("Do you want to paste over current selection?", _
                "Cut Example", MessageBoxButtons.YesNo) = DialogResult.No Then
                ' Move selection to the point after the current selection and paste.
                textBox1.SelectionStart = textBox1.SelectionStart + _
                    textBox1.SelectionLength
            End If
        End If 
        ' Paste current text in Clipboard into text box.
        textBox1.Paste()
    End If
End Sub

Private Sub Menu_Undo(sender As System.Object, e As System.EventArgs)
    ' Determine if last operation can be undone in text box.   
    If textBox1.CanUndo = True Then
        ' Undo the last operation.
        textBox1.Undo()
        ' Clear the undo buffer to prevent last action from being redone.
        textBox1.ClearUndo()
    End If
End Sub

示例2Example 2

下面的示例SelectionStart ReadOnly通过TextBox 将的属性设置为第一个来设置的属性。FocusThe following example sets the SelectionStart property of a TextBox that is ReadOnly by giving it the Focus first.

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.button1.Click += new System.EventHandler(this.ButtonClickWork);
    }

    private void ButtonClickWork(object sender, EventArgs e)
    {
        this.textBox1.Text = "Hello world!";
        this.textBox1.ReadOnly = true;

        this.textBox1.Focus();
        this.textBox1.SelectionStart = this.textBox1.SelectionStart + 1;
        this.textBox1.SelectionLength = 1;
    }
}
Public Class Form1

    Private Sub ButtonClickWork(ByVal sender As System.Object, ByVal e As System.EventArgs) _
        Handles Button1.Click

        Me.TextBox1.Text = "Hello world!"
        Me.TextBox1.ReadOnly = True

        Me.TextBox1.Focus()
        Me.TextBox1.SelectionStart = Me.TextBox1.SelectionStart + 1
        Me.TextBox1.SelectionLength = 1
    End Sub
End Class

注解

如果在控件中未选择任何文本,此属性将指示新文本的插入点或插入符号。If no text is selected in the control, this property indicates the insertion point, or caret, for new text. 如果将此属性设置为超出控件中文本长度的位置,则所选内容的起始位置将被置于最后一个字符之后。If you set this property to a location beyond the length of the text in the control, the selection start position will be placed after the last character. 在文本框控件中选择文本时,更改此属性可能会降低SelectionLength属性的值。When text is selected in the text box control, changing this property might decrease the value of the SelectionLength property. 如果控件中由SelectionStart属性指示的位置之后的剩余文本小于SelectionLength属性的值SelectionLength ,则自动减小属性的值。If the remaining text in the control after the position indicated by the SelectionStart property is less than the value of the SelectionLength property, the value of the SelectionLength property is automatically decreased. SelectionStart属性的值从不导致SelectionLength属性增加。The value of the SelectionStart property never causes an increase in the SelectionLength property.

您可以通过设置SelectionStart SelectionLength和属性,以编程方式在文本框中移动选择。You can programmatically move the selection within the text box by setting the SelectionStart and the SelectionLength properties.

您可以通过在文本框中将插入符号的位置设置SelectionStart为要在其中移动插入符号的位置,并将该SelectionLength属性的值设置为零(0),来以编程方式移动插入符号。You can programmatically move the caret within the text box by setting the SelectionStart to the position within the text box where you want the caret to move to and set the SelectionLength property to a value of zero (0).

若要移动选定内容或插入符号,必须具有焦点。TextBoxThe TextBox must have focus in order for the selection or the caret to be moved. 可以设置SelectionStart的属性TextBoxReadOnly 方法Focus是先将其赋予。You can set the SelectionStart property of a TextBox that is ReadOnly by giving it the Focus first.

适用于