.net - How to make custom DataGridViewComboBox dependent only on its DataGridViewComboBoxColumn? -

popular way (1, 2) custom painting of items in datagridviewcombobox handling of event datagridview1.editingcontrolshowing , setting drawitem event handlers there:

private void datagridview1_editingcontrolshowing(     object sender,     datagridvieweditingcontrolshowingeventargs e) {     theboxcell = (combobox) e.control;     theboxcell.drawitem += theboxcell_drawitem;     theboxcell.drawmode = drawmode.ownerdrawvariable; } 

you see wrong: uses control-level event handle work columns. if have 50+ datagridviews? painting of custom combo boxes should handled per column instance, leaving control level intact.

minimal implementation of per-column handling below. problem have ondrawitem() method not getting called. missing? (you can see fuchsia background override the same class working.)

(to reproduce, paste following class file , add column of type datagridviewcustompaintcomboboxcolumn datagridview1.)

public class datagridviewcustompaintcomboboxcolumn : datagridviewcomboboxcolumn {     public datagridviewcustompaintcomboboxcolumn()     {         base.new();         celltemplate = new datagridviewcustompaintcomboboxcell();     }  }  public class datagridviewcustompaintcomboboxcell : datagridviewcomboboxcell {     public override type edittype {         { return typeof(datagridviewcustompaintcomboboxeditingcontrol); }     }      protected override void paint(...)     {         //painting stuff incative cells here - works     }  }  public class datagridviewcustompaintcomboboxeditingcontrol : datagridviewcomboboxeditingcontrol {     public override color backcolor { // property override testing         { return color.fuchsia; }    // test value works expected         set { base.backcolor = value; }     }      protected override void onpaint(painteventargs e) // never called - why?     {         base.onpaint(e)     }      protected override void ondrawitem(drawitemeventargs e)  // never called - why?     {         base.ondrawitem(e)     } } 

the problem have ondrawitem() method not getting called. missing?

what see inside focussed datagridviewcomboboxcell pretty 'real' combobox , need reference in order hook drawitem event! (you can have controls collection of dgv see there 1 more when comboboxcell has focus.. datagridviewcomboboxeditingcontrol directly descended combobox )

note: 1 difference out of box combbox is has set drawmode = ownerdrawvariable default. if want replace create yourself, don't forget set in code!

looks missing!

if can create own datagridviewcomboboxeditingcontrol , make appear in dgv you're set.

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an alternative model use sort of 'decorator', implements custom drawing columns register it.

dgvcombboxpainter.register(datagridview dgv, stringorint columnnameorindex..) 

in registration function hook necessary dgv methods, editingcontrolshowing @ combobox see, when dgv has focus , cellpainting other cases.

the decorator can static , needs 1 combobox columns have registered, 1 can have focus @ time..

if can handle painting code in decorator better. events can reach datagridview via sender , cells' properties via datagridviewcellpaintingeventargs parameter..

you can put reference current cell combobox reference's tag:

theboxcell.tag = datagridview1.currentcell; 

if want provide individual delegates call in paint event(s) when registering. have keep list of those, maybe in dictionary..