在许多工程设计和图纸制作中，文字元素扮演着至关重要的角色。特别是带有上下标的文字，在展示特定信息（如化学式、数学公式）时尤为重要。本文将指导读者如何在MicroStation软件中，通过编程创建带有上下标的文字元素。

文本样式决定了文字元素的样子，Mstn中我们在如下所示的对话框中订制文本样式：

可以看到文字样式包含了很多设置，在Mstn的.Net编程框架中有如下所示的枚举类型：

namespace Bentley.DgnPlatformNET
{
    public enum TextStyleProperty
    {
        InvalidProperty = 0,
        Color = 1,
        ColorFlag = 2,
        Font = 3,
        ShxBigFont = 4,
        Width = 5,
        Height = 6,
        Slant = 7,
        Underline = 8,
        Overline = 9,
        Italics = 10,
        Bold = 11,
        Superscript = 12,
        Subscript = 13,
        Backgroundstyleflag = 14,
        Backgroundstyle = 15,
        Backgroundweight = 16,
        Backgroundcolor = 17,
        Backgroundfillcolor = 18,
        Backgroundborder = 19,
        Underlinestyle = 20,
        Underlineweight = 21,
        Underlinecolor = 22,
        Underlinestyleflag = 23,
        UnderlineOffset = 24,
        Overlinestyle = 25,
        Overlineweight = 26,
        Overlinecolor = 27,
        Overlinestyleflag = 28,
        OverlineOffset = 29,
        LineSpacing = 30,
        FixedSpacing = 31,
        LineOffset = 32,
        InterCharSpacing = 33,
        DgnLineSpacingType = 34,
        AcadInterCharSpacing = 35,
        Justification = 36,
        FullJustification = 38,
        LineLength = 39,
        Backwards = 41,
        Upsidedown = 42,
        Fractions = 43,
        Vertical = 45,
        RightToLeft = 47
    }
}

Mstn SDK中用类型DgnTextStyle来表示文字样式，在这个类型下有多个名为SetProperty的重载函数，我们调用这些函数可以修改文本样式的设置。 这些函数的第一个参数都是TextStyleProperty类型，通过这个参数可以指定要修改哪个设置。我们将Superscript和Subscript这两个属性设置为True

就可以创建出上下标文字来。如下代码完整演示了如何创建带有上标的文字元素：

                DgnModel dgnModel = Session.Instance.GetActiveDgnModel();
                DgnFile dgnFile = Session.Instance.GetActiveDgnFile();
                DgnTextStyle txtStyle = DgnTextStyle.GetSettings(dgnFile);
                TextBlock txtBlock = new TextBlock(txtStyle, dgnModel);
                txtBlock.AppendText("This is a demo Text");
                txtStyle.SetProperty(TextStyleProperty.Superscript, true);
                RunProperties runProp = new RunProperties(txtStyle, dgnModel);
                txtBlock.SetRunPropertiesForAdd(runProp);
                txtBlock.AppendText("Superscript");
                TextHandlerBase txtHandler = TextHandlerBase.CreateElement(null, txtBlock);
                txtHandler.AddToModel();