TextBoxBase.SelectionStart 属性

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

获取或设置文本框中选定的文本起始点。

public:
 property int SelectionStart { int get(); void set(int value); };

[System.ComponentModel.Browsable(false)]
public int SelectionStart { get; set; }

[<System.ComponentModel.Browsable(false)>]
member this.SelectionStart : int with get, set

Public Property SelectionStart As Integer

属性值

Int32

文本框中选定的文本的起始位置。

属性

BrowsableAttribute

例外

ArgumentOutOfRangeException

赋给的值小于零。

示例

示例 1

下面的代码示例使用 TextBox，一个派生类。 它为MenuItem执行剪切、复制、粘贴和撤消操作的对象提供Click事件处理程序。 此示例要求已创建名为 TextBox 的 textBox1 控件。

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 2

下面的示例通过提供Focus第一个 ReadOnlyTextBox 来设置 SelectionStart 的 属性。

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，则此属性指示新文本的插入点或插入点。 如果将此属性设置为超出控件中文本长度的位置，则选择开始位置将放在最后一个字符之后。 在文本框控件中选择文本时，更改此属性可能会减小属性的值 SelectionLength 。 如果 控件中属性所 SelectionStart 指示的位置之后的剩余文本小于 属性的值 SelectionLength ，则属性的值 SelectionLength 将自动减小。 属性的值 SelectionStart 从不会导致属性增加 SelectionLength 。

可以通过设置 SelectionStart 和 SelectionLength 属性，以编程方式在文本框中移动所选内容。

可以通过编程方式移动文本框中的插入点，方法是将 设置为 SelectionStart 希望插入点移动到的文本框中的位置，并将 属性设置为 SelectionLength 零 (0) 的值。

TextBox必须具有焦点才能移动所选内容或插入点。 可以通过提供Focus第一个 ReadOnlyTextBox 来设置 SelectionStart 的 属性。