Help Needed! Really Stuck. C# dvents & null delegates

[c#2006user]

Hi everyone.

i know there is a lot of code and ive reduced it as much as i could,
its a bit much to ask but i am really stuck!
i've been at this for a week! this is converted from vb to c# and
something has gone wrong with the events as the original code used
"WithEvents " and "Handles" keywords.

basically when i debug and get to the mainList_Select ed(............ .)
method the MainListSelecte dEvent is null and i think this is where the
problem is.

if anyone could help id be really greatful!!

This is the main class and this is the method that is called

private void displayHomePage ()
{
try
{
Page pg;
while (history.Count > 0)
{
pg = (Page) history.Pop();
pg.Dispose();
}
if (currentPage != null)
{
currentPage.Dis pose();
currentPage = null;
}
HomePage newPage = new HomePage();
currentPage = newPage;
MusicXP.frmMain X = this;
newPage.Display Page(ref X);
}
catch (System.Excepti on ex)
{
ErrorHandler.Ge nericHandler(ex );
}

}

----------------------------------------------------------------------------------------------------------------------------------

public abstract class Page : IDisposable
{
protected dmControls.imag eList albumList;
protected dmControls.deta ilImageList detailList;
protected dmControls.List Control mainList;
protected dmControls.List Control sideList;
protected dmControls.VisK eys softKeyboard;
protected frmMain theForm;
protected int albumListSelect edIndex;
protected int detailListSelec tedIndex;
protected int mainListSelecte dIndex;
protected int sideListSelecte dIndex;
protected string hasFocus;
protected string softKeyboardTex t;

//I took out the main events and delegates that were created in
the conversion, this i think is where the problem
//The MainListSelecte dEvent is Null When it is called in the
mainList_Select ed.

public delegate void MainListSelecte dEventHandler(s tring
sSelected, object Data);
public MainListSelecte dEventHandler MainListSelecte dEvent; //=
new MainListSelecte dEventHandler(m ainList_Selecte d);
public event MainListSelecte dEventHandler MainListSelecte d
{
add { MainListSelecte dEvent =
(MainListSelect edEventHandler) System.Delegate .Combine(MainLi stSelectedEvent ,
value); }
remove { MainListSelecte dEvent =
(MainListSelect edEventHandler) System.Delegate .Remove(MainLis tSelectedEvent,
value); }
}

public void mainList_Select ed(string sSelected, object Data)
{
// object tmpObject = new object();
//Data = tmpObject;
Sounds.PlaySele ctSound();
if (MainListSelect edEvent != null)
MainListSelecte dEvent(sSelecte d, Data);
}

"The Rest of the Delegates are in here"
"The Rest of the Event are in here"

public virtual void DisplayPage(ref frmMain myForm)
{
myForm.currentP age = this;
this.albumList = myForm.albumLis t;
this.detailList = myForm.detailLi st;
this.mainList = myForm.listNavi gation;
this.sideList = myForm.sideNavi gation;
this.softKeyboa rd = myForm.softKeyb oard;
this.theForm = myForm;
this.mainList.L eaveControl += new
dmControls.List Control.LeaveCo ntrolEventHandl er(mainList_Lea veControl);
this.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d);
this.mainList.S electionChanged += new
dmControls.List Control.Selecti onChangedEventH andler(mainList _SelectionChang ed);
"the Rest of the assignment are in here........... ..."
}

public Page()
{

}

public void Dispose()
{
this.Dispose();
}
}

---------------------------------------------------------------------------------------------------------------------------------------------------

class HomePage : NavigationPage
{

public HomePage()
{

string[] navArray = new string[6];
navArray[0] = "Recent Albums";
navArray[1] = "Browse All Albums";
navArray[2] = "Browse Artists";
navArray[3] = "Playlists" ;
navArray[4] = "Scan Music Files";
navArray[5] = "Settings";

base.navArray = navArray;
base.itemCount = navArray.GetLen gth(0);
//base.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d);
}

private void HomePage_MainLi stSelected(stri ng sSelected, object
Data)
{
stuff in here........... ............... ..
}

public override void SavePageState(r ef frmMain myForm)
{
base.SavePageSt ate(ref myForm);
}

public override void DisplayPage(ref frmMain myForm)
{
base.DisplayPag e(ref myForm);
myForm.wmp.Visi ble = true;
myForm.SetUpHom eView();
}

}
}

[Nick Hounsome]

- You never attach a handler to the event MainListSelecte d.
- I see no reason for all the ref parameters.
You only need ref for a form if you want to write use myForm as an
L-value NOT when you are just calling its members or properties.
- You've gone to a lot of trouble to write code that the compiler will do
for you - All you need is:

public event MainListSelecte dEventHandler MainListSelecte d;
public void mainList_Select ed(string sSelected, object Data)
{
//........
if (MainListSelect edEvent != null)
MainListSelecte dEvent(.....);
}

The compiler creates the delegate and add and remove methods.

- You have commented out an initialization of your delegate which would have
assigned it the method that actually calls it - this would have been
infinitely recursive - I have no idea what you really intended.
- IMHO the whole thing is a bit of a mess because of your naming - You have
something that isn't an event called MainListSelecte dEvent; You have an
event called Selected on something called mainList and an event called
MainListSelecte d on the page.

"c#2006user " <ht*******@hotm ail.com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com.. .

Hi everyone.

i know there is a lot of code and ive reduced it as much as i could,
its a bit much to ask but i am really stuck!
i've been at this for a week! this is converted from vb to c# and
something has gone wrong with the events as the original code used
"WithEvents " and "Handles" keywords.

basically when i debug and get to the mainList_Select ed(............ .)
method the MainListSelecte dEvent is null and i think this is where the
problem is.

if anyone could help id be really greatful!!

This is the main class and this is the method that is called

private void displayHomePage ()
{
try
{
Page pg;
while (history.Count > 0)
{
pg = (Page) history.Pop();
pg.Dispose();
}
if (currentPage != null)
{
currentPage.Dis pose();
currentPage = null;
}
HomePage newPage = new HomePage();
currentPage = newPage;
MusicXP.frmMain X = this;
newPage.Display Page(ref X);
}
catch (System.Excepti on ex)
{
ErrorHandler.Ge nericHandler(ex );
}

}

----------------------------------------------------------------------------------------------------------------------------------

public abstract class Page : IDisposable
{
protected dmControls.imag eList albumList;
protected dmControls.deta ilImageList detailList;
protected dmControls.List Control mainList;
protected dmControls.List Control sideList;
protected dmControls.VisK eys softKeyboard;
protected frmMain theForm;
protected int albumListSelect edIndex;
protected int detailListSelec tedIndex;
protected int mainListSelecte dIndex;
protected int sideListSelecte dIndex;
protected string hasFocus;
protected string softKeyboardTex t;

//I took out the main events and delegates that were created in
the conversion, this i think is where the problem
//The MainListSelecte dEvent is Null When it is called in the
mainList_Select ed.

public delegate void MainListSelecte dEventHandler(s tring
sSelected, object Data);
public MainListSelecte dEventHandler MainListSelecte dEvent; //=
new MainListSelecte dEventHandler(m ainList_Selecte d);
public event MainListSelecte dEventHandler MainListSelecte d
{
add { MainListSelecte dEvent =
(MainListSelect edEventHandler) System.Delegate .Combine(MainLi stSelectedEvent ,
value); }
remove { MainListSelecte dEvent =
(MainListSelect edEventHandler) System.Delegate .Remove(MainLis tSelectedEvent,
value); }
}

public void mainList_Select ed(string sSelected, object Data)
{
// object tmpObject = new object();
//Data = tmpObject;
Sounds.PlaySele ctSound();
if (MainListSelect edEvent != null)
MainListSelecte dEvent(sSelecte d, Data);
}

"The Rest of the Delegates are in here"
"The Rest of the Event are in here"

public virtual void DisplayPage(ref frmMain myForm)
{
myForm.currentP age = this;
this.albumList = myForm.albumLis t;
this.detailList = myForm.detailLi st;
this.mainList = myForm.listNavi gation;
this.sideList = myForm.sideNavi gation;
this.softKeyboa rd = myForm.softKeyb oard;
this.theForm = myForm;
this.mainList.L eaveControl += new
dmControls.List Control.LeaveCo ntrolEventHandl er(mainList_Lea veControl);
this.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d);
this.mainList.S electionChanged += new
dmControls.List Control.Selecti onChangedEventH andler(mainList _SelectionChang ed);
"the Rest of the assignment are in here........... ..."
}

public Page()
{

}

public void Dispose()
{
this.Dispose();
}
}

---------------------------------------------------------------------------------------------------------------------------------------------------

class HomePage : NavigationPage
{

public HomePage()
{

string[] navArray = new string[6];
navArray[0] = "Recent Albums";
navArray[1] = "Browse All Albums";
navArray[2] = "Browse Artists";
navArray[3] = "Playlists" ;
navArray[4] = "Scan Music Files";
navArray[5] = "Settings";

base.navArray = navArray;
base.itemCount = navArray.GetLen gth(0);
//base.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d);
}

private void HomePage_MainLi stSelected(stri ng sSelected, object
Data)
{
stuff in here........... ............... ..
}

public override void SavePageState(r ef frmMain myForm)
{
base.SavePageSt ate(ref myForm);
}

public override void DisplayPage(ref frmMain myForm)
{
base.DisplayPag e(ref myForm);
myForm.wmp.Visi ble = true;
myForm.SetUpHom eView();
}

}
}

[c#2006user]

Thanks for thaking the time to reply Nick,
This is mostly auto-converted code from a vb.net project and i presume
that is why its
so overly complex/messy and hence why im so confused. (i could find no
examples of delegates and events that matched what i got from the
converter!)

Anyway I will try your suggestion and comment out the stuff you think i
dont need.

[c#2006user]

ok i tried reducing it to

public delegate void MainListSelecte dEventHandler(s tring sSelected,
object Data);
public event MainListSelecte dEventHandler MainListSelecte dEvent ;

this.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d); //in
the DisplayPage method

public void mainList_Select ed(string sSelected, object Data)
{
if (MainListSelect edEvent != null)
MainListSelecte dEvent(sSelecte d, Data);
}

but it still jumps over MainListSelecte dEvent(sSelecte d, Data);
because its null.

any other ideas nick or anyone.
thanks again.

[Chris Dunaway]

c#2006user wrote:

ok i tried reducing it to

public delegate void MainListSelecte dEventHandler(s tring sSelected,
object Data);
public event MainListSelecte dEventHandler MainListSelecte dEvent ;
this.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d); //in
the DisplayPage method

The event variable is called MainListSelecte dEvent so I think the line
above should be:

this.mainList.M ainListSelected Event += new
MainListSelecte dEventHandler(m ainList_Selecte d);

[Nick Hounsome]

"Chris Dunaway" <du******@gmail .com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com.. .

c#2006user wrote:

ok i tried reducing it to

public delegate void MainListSelecte dEventHandler(s tring sSelected,
object Data);
public event MainListSelecte dEventHandler MainListSelecte dEvent ;

this.mainList.S elected += new
dmControls.List Control.Selecte dEventHandler(m ainList_Selecte d); //in
the DisplayPage method

The event variable is called MainListSelecte dEvent so I think the line
above should be:

this.mainList.M ainListSelected Event += new
MainListSelecte dEventHandler(m ainList_Selecte d);

No - he means it. This is what I meant earlier about confusing naming - he
wants page.mainList.S elected to trigger page.MainListSe lectedEvent -
confusing naming and not very OO.

There has to be a line of code somewhere saying page.MainListSe lectedEvent
+= something. Where (and when) is it?

[c#2006user]

i done this and it seemed to work

MainListSelecte dEvent += new
MainListSelecte dEventHandler(m ainList_Selecte d);

thanks a million for your help

[Nick Hounsome]

"c#2006user " <ht*******@hotm ail.com> wrote in message
news:11******** *************@j 33g2000cwa.goog legroups.com...

i done this and it seemed to work

MainListSelecte dEvent += new
MainListSelecte dEventHandler(m ainList_Selecte d);

thanks a million for your help

I don't see how that can work because mainList_Select ed calls the
MainListSelecte dEvent according to your posting and this would result in a
infinite recursion