Ticklish Techs

There is a known issue in the current version of the DSL Tools while dealing with custom TypeConverters or custom TypeDescriptors:

1.10 TypeConverters and TypeDescriptors are not picked up during the build process or during toolbox initialization.
When adding a custom TypeConverter or TypeDescriptor and then building the DSL, the TypeConvertor or TypeDescriptor is not picked up. The workaround is to rebuild the solution with a clean build.

[see Known Issues for Microsoft Visual Studio 2008 SDK 1.0]

Some time ago I posted a workaround for this problem with the TypeConverter, but today a realized that this workaround does not work with the same issue for TypeDescriptors.

Imagine some class with the following attribute:

[TypeDescriptionProvider(typeof(MyClassTypeDescriptionProvider))]
public partial class MyClass : ModelElement
{}

The corresponding TypeDescriptor (provided by the MyClassTypeDescriptionProvider class) is loaded only the first time you build or rebuild your solution. Every time you start Visual Studio after that, this attribute seems to be ignored.

Fortunately there is another way to glue TypeDescriptors to your classes using a static method of the TypeDescriptor class at runtime:

TypeDescriptor.AddProvider(
   new MyClassTypeDescriptionProvider(), typeof(MyClass));

I think a good place for this code is the static constructor of the MyClass type:

partial class MyClass
{
    static MyClass()
    {
        TypeDescriptor.AddProvider(
            new MyClassTypeDescriptionProvider(),
            typeof(MyClass));
    }
}

Another interesting point is: Not only custom TypeDescriptors you write yourself are affected by this problem, also the TypeDescriptors that are generated by the DSL-Tools from your DslDefintion have to struggle with it:

In the DSL Explorer you can define custom TypeDescriptors for each Domain Class and each Shape. Even these TypeDescriptors will not be loaded after the first run. In other words: the definition of TypeDescriptors in the DSL Explorer is pretty useless as long as you do not add the three lines of code to each class. Of course this is something one can automate! 🙂 I stole some code from PropertiesGrid.tt and added a few lines to create the RegisterTypeDescriptor.tt. Just add this file to your Dsl Project in the GeneratedCode folder and all TypeDescriptors defined in the DSL Explorer will be loaded every time you start your project.