public bool SetNewParameterToInstanceWall(UIApplication app, DefinitionFile myDefinitionFile)
{
    // create a new group in the shared parameters file
    DefinitionGroups myGroups = myDefinitionFile.Groups;
    DefinitionGroup myGroup = myGroups.Create("MyParameters1");

    // create an instance definition in definition group MyParameters
    ExternalDefinitionCreationOptions option = new ExternalDefinitionCreationOptions("Instance_ProductDate", ParameterType.Text);
    // Don't let the user modify the value, only the API
    option.UserModifiable = false;
    // Set tooltip
    option.Description = "Wall product date";
    Definition myDefinition_ProductDate = myGroup.Definitions.Create(option);

    // create a category set and insert category of wall to it
    CategorySet myCategories = app.Application.Create.NewCategorySet();
    // use BuiltInCategory to get category of wall
    Category myCategory = Category.GetCategory(app.ActiveUIDocument.Document, BuiltInCategory.OST_Walls);


    myCategories.Insert(myCategory);

    //Create an instance of InstanceBinding
    InstanceBinding instanceBinding = app.Application.Create.NewInstanceBinding(myCategories);

    // Get the BingdingMap of current document.
    BindingMap bindingMap = app.ActiveUIDocument.Document.ParameterBindings;

    // Bind the definitions to the document
    bool instanceBindOK = bindingMap.Insert(myDefinition_ProductDate,
                                    instanceBinding, BuiltInParameterGroup.PG_TEXT);
    return instanceBindOK;
}

Public Function SetNewParameterToInstanceWall(app As UIApplication, myDefinitionFile As DefinitionFile) As Boolean
   ' create a new group in the shared parameters file
   Dim myGroups As DefinitionGroups = myDefinitionFile.Groups
   Dim myGroup As DefinitionGroup = myGroups.Create("MyParameters1")

   ' create an instance definition in definition group MyParameters
   Dim [option] As New ExternalDefinitionCreationOptions("Instance_ProductDate", ParameterType.Text)
   ' Don't let the user modify the value, only the API
   [option].UserModifiable = False
   ' Set tooltip
   [option].Description = "Wall product date"
   Dim myDefinition_ProductDate As Definition = myGroup.Definitions.Create([option])

   ' create a category set and insert category of wall to it
   Dim myCategories As CategorySet = app.Application.Create.NewCategorySet()
   ' use BuiltInCategory to get category of wall
   Dim myCategory As Category = Category.GetCategory(app.ActiveUIDocument.Document, BuiltInCategory.OST_Walls)


   myCategories.Insert(myCategory)

   'Create an instance of InstanceBinding
   Dim instanceBinding As InstanceBinding = app.Application.Create.NewInstanceBinding(myCategories)

   ' Get the BingdingMap of current document.
   Dim bindingMap As BindingMap = app.ActiveUIDocument.Document.ParameterBindings

   ' Bind the definitions to the document
   Dim instanceBindOK As Boolean = bindingMap.Insert(myDefinition_ProductDate, instanceBinding, BuiltInParameterGroup.PG_TEXT)
   Return instanceBindOK
End Function