How to add a Hyperlabel to your forms in Visual Studi= o.
Audience: VO developers moving to C# or Vulcan.
The Hyperlabel class is a very useful concept introdu=
ced by
CA in the Visual Objects class library in version 1.0. It is used for all =
kinds
of identification purposes and can easily be extended with all kinds of
properties that make sense in your framework. An example of this is adding=
a
help-identifier. For one of our recent projects we wanted to add exactly t=
hat,
a help identifier unique to each form and a human readable and formatted n=
ame, preferably to be edited in the
form-editor as properties. This also required the introduction of a form b=
ase class
to be used by every form in the application. So we went searching for the =
‘Inherit
from’ property in Visual Studio and .Net and could not find it. This=
is
not bad news how ever, Visual Studio has other ways to achieve the same go=
als.
What we got for free when we started exploring this is the concept of Visu=
al
Inheritance where an inherited form really exposes all visual aspects of t=
he
base class even in the form editor.
We start out by creating a form in Visual Studio is y= ou normally would for the purpose of the demo I added a label (fixedtext cont= rol) and a button, as well as a button click event handler to be used for testi= ng our Hyperlabel (see figure 1).
Figure 1, Base form design
The next task is implementing the Hyperlabel class and making it available in the form editor. In Visual Studio this can be done = in code, no need to edit any config files that need to be distributed.
The .net framework has a component class that implements everything for such a relatively simple ‘component’. A component is an object that g= ets added to your form but does not have a runtime user interface (that would = be a (user)control). So all we need to do is create a class that inherits from component and implement the public properties we want to support, below is the actual co= de:
public=
partial class SOHyperLabel : Component
{
private string _name;
private string
_helpcontext;
private string
_description;
private string
_caption;
public string Caption
{
=
;
get { =
return
_caption; }
=
;
set { _caption =3D value; }
}
public string
Description
{
=
;
get { =
return
_description; }
=
;
set { _description =3D value; }
}
public string
HelpContext
{
=
;
get { =
return
_helpcontext; }
=
;
set { _helpcontext =3D value; }
}
public string Name
{
=
;
get { =
return
_name; }
=
;
set { _name =3D value;
}
}
public SOHyperLabel()
{
=
;
InitializeComponent();
}
public SOHyperLabel(IContainer
container)
{
=
;
container.Add(this);
=
;
InitializeComponent();
}
}
As soon as a class that inherits from component is co= mpiled or is part of a dll in your project it will also appear as an available component in the toolbox for the form editor (see figure 2).
Figure 2, Hyperlabel component in the designer
So now we can drag and drop a Hyperlabel on the form = and it will appear in the component tray of our base form.
In figure 3 you can see that it also automatically ad= ds all fields as editable properties to the property window for the Hyperlabel component.
Figure 3, property window
You can also apply attributes, for example to hide so= me fields: [Browsable(fa= lse)], apply default values or create categories in the property window (to find = out more about this read this entry on msdn).=
=
Note that
after dropping the component on the base form the Modifier is private which
will prevent it from being accessible in subclasses, so we need to change =
the
modifier to public.
= To test our component and base form we can now create a new form by adding an item to = our project of type Inherited Form (figure 4).
Figure 4, Inherited Form
This will present a picklist of forms in this solutio= n and all we need to this is pick our BaseForm class.
Figure 5, List of forms to pick from
AS you can see in figure 6 the editor now nicely disp= lays the visual design of the base form and includes the Hyperlabel component.<= /p>
Figure 6, Subclassed form with component
You will notice that the controls and components that= are actually in the base form cannot be edited or moved, yet you can now set t= he actual values for the Hyperlabel component that apply to this subclassed f= orm.
You could now easily implement specific methods on th= e base class level for example to display a context sensitive help window based o= n the Hyperlabel HelpContext property of the subclassed form. Below a test metho= d, we’ll leave the help topic for another article.
{
=
;
this.label1.Text =3D this.soHyperLabel1.HelpContext;
}
© 2007
Ed Richard
Software Objectives
(Ed@SoftwareObjectives.com.au) <=
o:p>