Dockpanel suite judgment window opened

Recently, a winform project has to be implemented. The layout should be like the following.

However, there is a problem, that is, to determine whether the window has been opened, read some of the onlineCode, Such:

Private   Void Shownewform ( Object Sender, eventargs E)
{
If (Finddocument ( " Baseform " ) =   Null )
{
Baseform childform =   New Baseform ();
Childform. Show (dockpanel1 );
}
Else
{
Form F = Finddocument ( " Baseform " ) As Form;
F. Focus ();
}
}

/// Search for opened windows in dockpanel
///   </Summary>
///   <Param name = "text"> Input window title </Param>
///   <Returns> Returned window </Returns>
Private Idockcontent finddocument ( String Text)
{
If (Dockpanel1.documentstyle = Documentstyle. systemmdi)
{
Foreach (Form In Mdichil.pdf)
If (Form. Text = Text)
Return Form As Idockcontent;

Return   Null ;
}
Else
{
Foreach (Idockcontent content In Dockpanel1.documents)
If (Content. dockhandler. tabtext = Text)
Return Content;

Return Null;
}
}

I believe I can understand the code!