Fonts are a bit of a tricky thing in the diagramming surface. First, there's no easy way to change the font for the whole diagram. You'll need to change things at an individual shape level.

You can change the font for all of the decorators on a shape (I've added the code for this below), but it's complicated by the fact that decorators are not ShapeFields, so you need to change the font information on each decorator. However, one of our planned changes is to convert inner decorators to ShapeFields, so that should fix this.

As for changing the parts of a compartment, you should be able to change the compartment header text and list item text fonts independently.

namespace CompanyName.ProjectName.TestLanguage.Designer {  #region Using directives  using System;  using System.Collections.Generic;  using Microsoft.VisualStudio.Modeling;  using System.Diagnostics;  using Microsoft.VisualStudio.Modeling.Utilities;  using System.Drawing;  using Microsoft.VisualStudio.Modeling.Diagrams;  #endregion  /// <summary>  /// ClassShape in the Class Diagram template.  /// </summary>  public partial class ClassShape  {   /// <summary>   /// Gets called whenever a shape is inserted into the diagram.   /// This is a good time to setup visuals, because all shapes,   /// decorators, compartments, shapefields, etc. have been created.   /// </summary>   public override void OnShapeInserted()   {    base.OnShapeInserted();    // Define the font change to make.    // In this case, make all decorators show bold, italic,    // and bigger sized text.    FontSettings fs = new FontSettings();    fs.Bold = true;    fs.Italic = true;    fs.Size = 0.185f;    foreach (ShapeDecorator decorator in this.Decorators)    {     // Only do this for all of the text decorators in this shape.     TextShapeDecorator shapeDec = decorator as TextShapeDecorator;     if (shapeDec != null)     {      shapeDec.StyleSet.OverrideFont(DiagramFonts.ShapeText, fs);     }    }    // Make the compartment header title bold, and    // the compartment item test italic.    FontSettings fsTitle = new FontSettings();    fsTitle.Bold = true;    FontSettings fsItem = new FontSettings();    fsItem.Italic = true;    foreach (ShapeElement shape in this.NestedChildShapes)    {     // Only do this for all of the compartments in this shape.     Compartment compartment = shape as Compartment;     if (compartment != null)     {      compartment.StyleSet.OverrideFont(DiagramFonts.ShapeTitle, fsTitle);      compartment.StyleSet.OverrideFont(DiagramFonts.ShapeText, fsItem);     }    }   }  } }

The code above should produce compartments with bold headers and italic item text. However, due to a bug both are italic. I've entered a bug against that, so that we can fix it, so that both are independent.