How to: Extend the Domain-Specific Language Designer

You can make extensions to the designer that you use to edit DSL Definitions. Types of extension that you can make include adding menu commands, adding handlers for drag and double-click gestures, and rules that are triggered when particular types of values or relationships change. The extensions can be packaged as a Visual Studio Integration Extension (VSIX) and distributed to other users.

For sample code and more information about this feature, see the Visual Studio Visualization and Modeling SDK (VMSDK) Web site.

Set up a project that contains the code of your extension, and a VSIX project that exports the project. Your solution can contain other projects that are incorporated into the same VSIX.

To create a DSL Designer Extension Solution

  1. Create a new project using the Class Library project template. In the New Project dialog box, click Visual C# and then in the middle window click Class Library.

    This project will contain the code of your extensions.

  2. Create a new project using the VSIX project template. In the New Project dialog box, expand Visual C#, click Extensibility, and then in the middle window select VSIX Project.

    Select Add to Solution.

    Source.extension.vsixmanifest opens in the VSIX manifest editor.

  3. Above the Content field, click Add Content.

  4. In the Add Content dialog box, set Select a Content Type to MEF Component, and set Project to your class library project.

  5. Click Select Editions and make sure that Visual Studio Ultimate is checked.

  6. Make sure that the VSIX project is the Startup project of the solution.

  7. In the class library project, add references to the following assemblies:

    Microsoft.VisualStudio.CoreUtility

    Microsoft.VisualStudio.Modeling.Sdk.11.0

    Microsoft.VisualStudio.Modeling.Sdk.Diagrams.11.0

    Microsoft.VisualStudio.Modeling.Sdk.DslDefinition.11.0

    Microsoft.VisualStudio.Modeling.Sdk.Integration.11.0

    System.ComponentModel.Composition

    System.Drawing

    System.Drawing.Design

    System.Windows.Forms

To test any of the extensions in this topic, build and run the solution. An experimental instance of Visual Studio opens. In this instance, open a DSL solution. Edit the DslDefinition diagram. The extension behavior can be seen.

To deploy the extensions to the main Visual Studio, and to other computers, follow these steps:

  1. Find the VSIX installation file, in your VSIX project in bin\*\*.vsix

  2. Copy this file to the target computer, and then in Windows Explorer (or File Explorer), double-click it.

    The Visual Studio Extension Manager opens to confirm that the extension has been installed.

To uninstall the extension, follow these steps:

  1. in Visual Studio, on the Tools menu, click Extension Manager.

  2. Select the extension and delete it.

To make a shortcut menu command appear on the DSL Designer surface or in the DSL Explorer window, write a class resembling the following.

The class must implement ICommandExtension and must have the attribute DslDefinitionModelCommandExtension.

using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Linq;
using Microsoft.VisualStudio.Modeling.Diagrams;
using Microsoft.VisualStudio.Modeling.Diagrams.ExtensionEnablement;
using Microsoft.VisualStudio.Modeling.DslDefinition;
using Microsoft.VisualStudio.Modeling.DslDefinition.ExtensionEnablement;
using Microsoft.VisualStudio.Modeling.DslDesigner;
using Microsoft.VisualStudio.Modeling.ExtensionEnablement;

namespace Fabrikam.SimpleDslDesignerExtension
{
  /// <summary>
  /// Command extending the DslDesigner.
  /// </summary>
  [DslDefinitionModelCommandExtension] 
  public class MyDslDesignerCommand : ICommandExtension
  {
    /// <summary>
    /// Selection Context for this command
    /// </summary>
    [Import]
    IVsSelectionContext SelectionContext { get; set; }

    /// <summary>
    /// Is the command visible and active?
    /// This is called when the user right-clicks.
    /// </summary>
    public void QueryStatus(IMenuCommand command)
    {
      command.Visible = true;
      // Is there any selected DomainClasses in the Dsl explorer?
      command.Enabled = 
        SelectionContext.AtLeastOneSelected<DomainClass>();

      // Is there any selected ClassShape on the design surface?
      command.Enabled |= 
        (SelectionContext.GetCurrentSelection<ClassShape>()
                .Count() > 0);
    }
    /// <summary>
    /// Executes the command 
    /// </summary>
    /// <param name="command">Command initiating this action</param>
    public void Execute(IMenuCommand command)
    {
      ...
    }
    /// <summary>
    /// Label for the command
    /// </summary>
    public string Text
    {
      get { return "My Command"; }
    }
  }
}

The code is similar to the code of the menu command.

[DslDefinitionModelGestureExtension]
 class MouseGesturesExtensions : IGestureExtension
 {
  /// <summary>
  /// Double-clicking on a shape representing a Domain model element displays this model element in a dialog box
  /// </summary>
  /// <param name="targetElement">Shape element on which the user has clicked</param>
  /// <param name="diagramPointEventArgs">event args for this double-click</param>
  public void OnDoubleClick(ShapeElement targetElement,
       DiagramPointEventArgs diagramPointEventArgs)
  {
   ModelElement modelElement = PresentationElementHelper.
        GetDslDefinitionModelElement(targetElement);
   if (modelElement != null)
   {
    MessageBox.Show(string.Format(
      "Double clicked on {0}", modelElement.ToString()), 
      "Model element double-clicked");
   }
  }


  /// <summary>
  /// Tells if the DslDesigner can consume the to-be-dropped information
  /// </summary>
  /// <param name="targetMergeElement">Shape on which we try to drop</param>
  /// <param name="diagramDragEventArgs">Drop event</param>
  /// <returns><c>true</c> if we can consume the to be dropped data, and <c>false</c> otherwise</returns>
  public bool CanDragDrop(ShapeElement targetMergeElement,
        DiagramDragEventArgs diagramDragEventArgs)
  {
   if (diagramDragEventArgs.Data.GetDataPresent(DataFormats.FileDrop))
   {
    diagramDragEventArgs.Effect = DragDropEffects.Copy;
    return true;
   }
   return false;
  }


  /// <summary>
  /// Processes the drop by displaying the dropped text
  /// </summary>
  /// <param name="targetMergeElement">Shape on which we dropped</param>
  /// <param name="diagramDragEventArgs">Drop event</param>
  public void OnDragDrop(ShapeElement targetDropElement, DiagramDragEventArgs diagramDragEventArgs)
  {
   if (diagramDragEventArgs.Data.GetDataPresent(DataFormats.FileDrop))
   {
    string[] droppedFiles = 
      diagramDragEventArgs.Data.
               GetData(DataFormats.FileDrop) as string[];
    MessageBox.Show(string.Format("Dropped text {0}",
        string.Join("\r\n", droppedFiles)), "Dropped Text");
   }
  }
 }

This handler needs a domain model to work correctly. We provide a simple domain model.

using System.Diagnostics;
using Microsoft.VisualStudio.Modeling;
using Microsoft.VisualStudio.Modeling.DslDefinition;
namespace Fabrikam.SimpleDslDesignerExtension
{
  /// <summary>
  /// Rule firing when the type of a domain model property is changed. The change is displayed
  /// in the debugger (Output window of the Visual Studio instance debugging this extension)
  /// </summary>
  [RuleOn(typeof(PropertyHasType))]
  public class DomainPropertyTypeChangedRule : RolePlayerChangeRule
  {
    /// <summary>
    /// Method called when the Type of a Domain Property 
    /// is changed by the user in a DslDefinition
    /// </summary>
    /// <param name="e"></param>
    public override void RolePlayerChanged(RolePlayerChangedEventArgs e)
    {
      // We are only interested in the type
      if (e.DomainRole.Id == PropertyHasType.TypeDomainRoleId)
      {
        PropertyHasType relationship = 
           e.ElementLink as PropertyHasType;
        DomainType newType = e.NewRolePlayer as DomainType;
        DomainType oldType = e.OldRolePlayer as DomainType;
        DomainProperty property = relationship.Property;

         // We write about the Type change in the debugguer
        Debug.WriteLine(string.Format("The type of the Domain property '{0}' of domain class '{1}' changed from '{2}' to '{3}'",
          property.Name,
          property.Class.Name,
          oldType.GetFullName(false),
          newType.GetFullName(false))
} }  }  );

The following code implements a simple model. Create a new GUID to replace the placeholder.

using System;
using System.ComponentModel.Composition;
using Microsoft.VisualStudio.Modeling;
using Microsoft.VisualStudio.Modeling.DslDefinition;
namespace Fabrikam.SimpleDslDesignerExtension
{
    /// <summary>
    /// Simplest possible domain model 
    /// needed only for extension rules. 
    /// </summary>
    [DomainObjectId(SimpleDomainModelExtension.DomainModelId)]
    public class SimpleDomainModelExtension : DomainModel
    {
        // Id of this domain model extension 
        // Please replace this with a new GUID:
        public const string DomainModelId = 
                  "00000000-0000-0000-0000-000000000000";

        /// <summary>
        /// Constructor for the domain model extension
        /// </summary>
        /// <param name="store">Store in which the domain model will be loaded</param>
        public SimpleDomainModelExtension(Store store)
            : base(store, new Guid(SimpleDomainModelExtension.DomainModelId))
        {

        }

        /// <summary>
        /// Rules brought by this domain model extension
        /// </summary>
        /// <returns></returns>
        protected override System.Type[] GetCustomDomainModelTypes()
        {
            return new Type[] {
                     typeof(DomainPropertyTypeChangedRule)
                              };
        }
    }


    /// <summary>
    /// Provider for the DomainModelExtension
    /// </summary>
    [Export(typeof(DomainModelExtensionProvider))]    [ProvidesExtensionToDomainModel(typeof(DslDefinitionModelDomainModel))]
    public class SimpleDomainModelExtensionProvider 
          : DomainModelExtensionProvider
    {
        /// <summary>
        /// Extension model type
        /// </summary>
        public override Type DomainModelType
        {
            get
            {
                return typeof(SimpleDomainModelExtension);
            }
        }

    }
}
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