C# 4 and .NET 4

Custom activities ❘ OC293
{
}
if (!(act is SequenceActivity))
return false;
}
return base.CanInsertActivities(insertLocation, activitiesToInsert);
}
protected override CompositeActivity OnCreateNewBranch()
{
return new SequenceActivity();
}
This Designer derives from ParallalActivityDesigner, which provides you with good design-time
behavior when adding child activities. You will need to override CanInsertActivities to return false if
any of the dropped activities is not a SequenceActivity. If all activities are of the appropriate type, you
can call the base class method, which makes some further checks on the activity types permitted within
your custom activity.
You should also override the OnCreateNewBranch method that is called when the user chooses the Add
Branch menu item. The Designer is associated with the activity by using the [Designer] attribute, as
shown here:
[Designer(typeof(DaysOfWeekDesigner))]
public class DaysOfWeekActivity: CompositeActivity
{
}
The design-time behavior is nearly complete; however, you also need to add a class that is derived from
ActivityToolboxItem to this activity, because that defines what happens when an instance of that activity
is dragged from the toolbox. The default behavior is simply to construct a new activity; however, in the
example you also want to create two default branches. The following code shows the toolbox item class in
its entirety:
[Serializable]
public class DaysOfWeekToolboxItem: ActivityToolboxItem
{
public DaysOfWeekToolboxItem(Type t)
: base(t)
{
this.DisplayName = "DaysOfWeek";
}
}
private DaysOfWeekToolboxItem(SerializationInfo info,
StreamingContext context)
{
this.Deserialize(info, context);
}
protected override IComponent[] CreateComponentsCore(IDesignerHost host)
{
CompositeActivity parent = new DaysOfWeekActivity();
parent.Activities.Add(new SequenceActivity());
parent.Activities.Add(new SequenceActivity());
}
return new IComponent[] { parent };
As shown in the code, the display name of the activity was changed, a serialization constructor was
implemented, and the CreateComponentsCore method was overridden.
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