'文本框选中显示
'TextBox1.SelectAll()选择所有文本
'textBox1.Text.Insert(start,strInsertText)指定位置添加文本
1 Private Sub TextBox1_MouseClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TextBox1.MouseClick

         Dim start As Integer = TextBox1.SelectionStart  '光标开始位置索引

         Dim SelectValue As String = TextBox1.SelectedText '选中文本的值

         Dim length As Integer = TextBox1.SelectedText.Trim.Length '选中文本的长度

         If length >  Then

             TextBox1.Select(start, length) '选中文本从光标到指定长度

         End If

     End Sub

'选中文本后右键弹出菜单栏
 1 Private Sub TextBox1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TextBox1.MouseDown

         If TextBox1.SelectedText.Trim.Length >  Then

             If e.Button = Windows.Forms.MouseButtons.Right Then

                 TextBox1.Enabled = False

                 TextBox1.ContextMenuStrip = ContextMenuStrip1

                 TextBox1.Enabled = True

             End If

         End If

     End Sub