textbox控件会根据里面显示的文字行数自动调整自己的大小

  '实现TextBox的高度自适应(MultiLine属性为ture情况下）
    '在设计时还应将TextBox的minimumSize设为（0，21）或其它非空值,可选设置maximumsize
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        'TextBox1 的行高
        Dim intLineHeight As Integer = Me.TextBox1.MinimumSize.Height - Me.TextBox1.Font.Size
        '获得行数
        Dim intLineCount As Integer = Me.TextBox1.GetLineFromCharIndex(TextBox1.Text.Length - 1) + 1
        '设置高度
        'Me.TextBox1.Height = intLineHeight * intLineCount + Me.TextBox1.Font.Size
        '如果有需要限制最大高度，用如下代码代替上面一行
        Dim intTBHeight As Integer = intLineHeight * intLineCount + Me.TextBox1.Font.Size
        If intTBHeight <= Me.TextBox1.MaximumSize.Height Then Me.TextBox1.Height = intTBHeight
    End Sub