LoadControl() and Constructor Parameters

[Sam Kuehn]

How do I accomplish the fallowing (is it even possible). Say I write a UserControl
"MyControl.ascx ". Now I use LoadControl("My Control.ascx"). But I really
want MyControl to require parameters in the constructor for example MyContorl
oMyControl = new MyContorl(emplo yeeid). However I need to load the control
at runtime so the have to call it this way LoadControl("My Control.ascx")
and I get an error that I have not supplied any parameter to the constructor.
Is there anyway around this? I guess I could change the control so that
I can insatiate it without supplying parameters and assigning the properties
later; but that doesn't seem like a very clean solution. Thanks in advance.

[Scott Allen]

Re: LoadControl() and Constructor Parameters

Controls have to have a paramerter-less constructor. You could use a
factory type pattern to keep a clean design. Perhaps even a static
method on the class like so:

MyUserControl uc = MyUserControl.C reate(param1, param2) { ... }


What do you think?

--
Scott

http://www.OdeToCode.com/blogs/scott/

On Thu, 10 Feb 2005 13:25:41 -0800, Sam Kuehn <samkuehn@hotma il.com>
wrote:
[color=blue]
>How do I accomplish the fallowing (is it even possible). Say I write a UserControl
>"MyControl.asc x". Now I use LoadControl("My Control.ascx"). But I really
>want MyControl to require parameters in the constructor for example MyContorl
>oMyControl = new MyContorl(emplo yeeid). However I need to load the control
>at runtime so the have to call it this way LoadControl("My Control.ascx")
>and I get an error that I have not supplied any parameter to the constructor.
> Is there anyway around this? I guess I could change the control so that
>I can insatiate it without supplying parameters and assigning the properties
>later; but that doesn't seem like a very clean solution. Thanks in advance.
>[/color]

[Sam Kuehn]

Re: LoadControl() and Constructor Parameters

Hello Scott,
That would work great if I didn't have to load the control at runtime. See
I don't know what UserContol I am going to add at design time. It is dependant
on user input at runtime. Therefore, I cannot call a method (or throw parameters
at the constructor for that matter). Also, are you saying that I couldn't
do something like:

public class MyControl: System.Web.UI.U serControl
{
//Constructor
MyControll(int employeeid){... ..}
}
Casue it seem that would work just fine.
[color=blue]
> Controls have to have a paramerter-less constructor. You could use a
> factory type pattern to keep a clean design. Perhaps even a static
> method on the class like so:
>
> MyUserControl uc = MyUserControl.C reate(param1, param2) { ... }
>
> What do you think?
>
> --
> Scott
> http://www.OdeToCode.com/blogs/scott/
> On Thu, 10 Feb 2005 13:25:41 -0800, Sam Kuehn <samkuehn@hotma il.com>
> wrote:
>[color=green]
>> How do I accomplish the fallowing (is it even possible). Say I write
>> a UserControl "MyControl.ascx ". Now I use
>> LoadControl("My Control.ascx"). But I really want MyControl to
>> require parameters in the constructor for example MyContorl
>> oMyControl = new MyContorl(emplo yeeid). However I need to load the
>> control at runtime so the have to call it this way
>> LoadControl("My Control.ascx") and I get an error that I have not
>> supplied any parameter to the constructor. Is there anyway around
>> this? I guess I could change the control so that I can insatiate it
>> without supplying parameters and assigning the properties later; but
>> that doesn't seem like a very clean solution. Thanks in advance.
>>[/color][/color]

[Scott Allen]

Re: LoadControl() and Constructor Parameters

Hi Sam:

See my notes inline.

On Thu, 10 Feb 2005 14:14:30 -0800, Sam Kuehn <samkuehn@hotma il.com>
wrote:
[color=blue]
>Hello Scott,
>That would work great if I didn't have to load the control at runtime. See
>I don't know what UserContol I am going to add at design time. It is dependant
>on user input at runtime. Therefore, I cannot call a method (or throw parameters
>at the constructor for that matter).[/color]

That's perfect for the factory pattern - it encapsulates all of the
logic needed to create and initialize an object, it also hides the
Type of the object being created. Some more details here:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/factopattern.asp

[color=blue]
>Also, are you saying that I couldn't
>do something like:
>
>public class MyControl: System.Web.UI.U serControl
>{
> //Constructor
> MyControll(int employeeid){... ..}
>}
>Casue it seem that would work just fine.
>[/color]

Unfortunately not. When the runtime creates an instance of the control
it does so with the paramerter-less ctor.

--
Scott

http://www.OdeToCode.com/blogs/scott/

[color=blue][color=green]
>> Controls have to have a paramerter-less constructor. You could use a
>> factory type pattern to keep a clean design. Perhaps even a static
>> method on the class like so:
>>
>> MyUserControl uc = MyUserControl.C reate(param1, param2) { ... }
>>
>> What do you think?
>>
>> --
>> Scott
>> http://www.OdeToCode.com/blogs/scott/
>> On Thu, 10 Feb 2005 13:25:41 -0800, Sam Kuehn <samkuehn@hotma il.com>
>> wrote:
>>[color=darkred]
>>> How do I accomplish the fallowing (is it even possible). Say I write
>>> a UserControl "MyControl.ascx ". Now I use
>>> LoadControl("My Control.ascx"). But I really want MyControl to
>>> require parameters in the constructor for example MyContorl
>>> oMyControl = new MyContorl(emplo yeeid). However I need to load the
>>> control at runtime so the have to call it this way
>>> LoadControl("My Control.ascx") and I get an error that I have not
>>> supplied any parameter to the constructor. Is there anyway around
>>> this? I guess I could change the control so that I can insatiate it
>>> without supplying parameters and assigning the properties later; but
>>> that doesn't seem like a very clean solution. Thanks in advance.
>>>[/color][/color]
>
>[/color]

[Hasani Blackwell]

Re: LoadControl() and Constructor Parameters

All ascxs have only 1 constructor. Maybe the class MyControl.ascx inherits
from has overloaded constructors, but the asp.net runtime will call the
default constructor. You're going to need to take a different approach. If
you want the control to know the employeeid, use the session or something.

"Sam Kuehn" <samkuehn@hotma il.com> wrote in message
news:1228796324 36423422339114@ msnews.microsof t.com...[color=blue]
> How do I accomplish the fallowing (is it even possible). Say I write a
> UserControl "MyControl.ascx ". Now I use LoadControl("My Control.ascx").
> But I really want MyControl to require parameters in the constructor for
> example MyContorl oMyControl = new MyContorl(emplo yeeid). However I need
> to load the control at runtime so the have to call it this way
> LoadControl("My Control.ascx") and I get an error that I have not supplied
> any parameter to the constructor. Is there anyway around this? I guess I
> could change the control so that I can insatiate it without supplying
> parameters and assigning the properties later; but that doesn't seem like
> a very clean solution. Thanks in advance.
>
>[/color]

[Sam Kuehn]

Re: LoadControl() and Constructor Parameters

Thanks! This is exactly the type of info I was looking for. I will try
and implment a solution using the factory pattern.
[color=blue]
> Hi Sam:
>
> See my notes inline.
>
> On Thu, 10 Feb 2005 14:14:30 -0800, Sam Kuehn <samkuehn@hotma il.com>
> wrote:
>[color=green]
>> Hello Scott,
>> That would work great if I didn't have to load the control at
>> runtime. See
>> I don't know what UserContol I am going to add at design time. It is
>> dependant
>> on user input at runtime. Therefore, I cannot call a method (or
>> throw parameters
>> at the constructor for that matter).[/color]
> That's perfect for the factory pattern - it encapsulates all of the
> logic needed to create and initialize an object, it also hides the
> Type of the object being created. Some more details here:
> http://msdn.microsoft.com/library/de...ry/en-us/dnbda
> /html/factopattern.as p
>[color=green]
>> Also, are you saying that I couldn't do something like:
>>
>> public class MyControl: System.Web.UI.U serControl
>> {
>> //Constructor
>> MyControll(int employeeid){... ..}
>> }
>> Casue it seem that would work just fine.[/color]
> Unfortunately not. When the runtime creates an instance of the control
> it does so with the paramerter-less ctor.
>
> --
> Scott
> http://www.OdeToCode.com/blogs/scott/[color=green][color=darkred]
>>> Controls have to have a paramerter-less constructor. You could use a
>>> factory type pattern to keep a clean design. Perhaps even a static
>>> method on the class like so:
>>>
>>> MyUserControl uc = MyUserControl.C reate(param1, param2) { ... }
>>>
>>> What do you think?
>>>
>>> --
>>> Scott
>>> http://www.OdeToCode.com/blogs/scott/
>>> On Thu, 10 Feb 2005 13:25:41 -0800, Sam Kuehn <samkuehn@hotma il.com>
>>> wrote:
>>>> How do I accomplish the fallowing (is it even possible). Say I
>>>> write a UserControl "MyControl.ascx ". Now I use
>>>> LoadControl("My Control.ascx"). But I really want MyControl to
>>>> require parameters in the constructor for example MyContorl
>>>> oMyControl = new MyContorl(emplo yeeid). However I need to load the
>>>> control at runtime so the have to call it this way
>>>> LoadControl("My Control.ascx") and I get an error that I have not
>>>> supplied any parameter to the constructor. Is there anyway around
>>>> this? I guess I could change the control so that I can insatiate
>>>> it without supplying parameters and assigning the properties later;
>>>> but that doesn't seem like a very clean solution. Thanks in
>>>> advance.
>>>>[/color][/color][/color]

[Sam Kuehn]

Re: LoadControl() and Constructor Parameters

I didn't want to call any Session stuff in my control. I was hoping not
to have to couple the control to this specific app that much. I would rather
pass the value in. Although the value I pass in will probably come form
the session object. Also all of the control in question do inherit from
a base control. Just for further claification here is the full picure of
what I am trying to do.

//The Base Control
namespace ExpenseReimburs ment.GUI.Contro ls.Add
{
public delegate void ItemAddedEventH andler(object sender, EventArgs ea);
public class BaseControl : System.Web.UI.U serControl
{
// ToDo: Create constructor with params
// public BaseControl(Sub CategoryEntity Subcategory)
// {
// _Subcategory = Subcategory;
// }
// private SubCategoryEnti ty _Subcategory;
// public SubCategoryEnti ty Subcategory
// {
// get
// {
// return _Subcategory;
// }
// set
// {
// _Subcategory = value;
// }
// }
#region Public Events
public event ItemAddedEventH andler ItemAdded;
protected virtual void OnItemAdded(Eve ntArgs ea)
{
if (ItemAdded != null)
ItemAdded(this, ea);
}
#endregion

#region Public Methods
public void AddItem(Expense ReportDetailEnt ity lineItem)
{
lineItem.Save() ;
OnItemAdded(new EventArgs());
}
public void AddItem(Expense ReportDetailCol lection lineItems)
{
lineItems.SaveM ulti();
OnItemAdded(new EventArgs());
}
#endregion

}

}

The actual control will depend on the type of expense they are adding for
example:

public class DefaultControl : BaseControl {} //the default control.

And is called form the "Master Page" like this:
private void LoadAddItemsCon trol(int Subcategoryid)
{
phAdd.Controls. Clear();
SubCategoryEnti ty ojbSubCategoryE ntity = new SubCategoryEnti ty(Subcategoryi d);
string control = "~/Controls/Add/Default.ascx";
if (ojbSubCategory Entity.Inputcon trol.ToString() != "")
control = "~/Controls/Add/" + ojbSubCategoryE ntity.Inputcont rol;
GUI.Controls.Ad d.BaseControl ctlAddDetail = (GUI.Controls.A dd.BaseControl) LoadControl(con trol);
ctlAddDetail.ID = "AddItem";
//Add Event Handler
ctlAddDetail.It emAdded += new GUI.Controls.Ad d.ItemAddedEven tHandler(this.I temAdded);
//Add control
phAdd.Controls. Add(ctlAddDetai l);
}
[color=blue]
> All ascxs have only 1 constructor. Maybe the class MyControl.ascx
> inherits from has overloaded constructors, but the asp.net runtime
> will call the default constructor. You're going to need to take a
> different approach. If you want the control to know the employeeid,
> use the session or something.
>
> "Sam Kuehn" <samkuehn@hotma il.com> wrote in message
> news:1228796324 36423422339114@ msnews.microsof t.com...
>[color=green]
>> How do I accomplish the fallowing (is it even possible). Say I write
>> a UserControl "MyControl.ascx ". Now I use
>> LoadControl("My Control.ascx"). But I really want MyControl to require
>> parameters in the constructor for example MyContorl oMyControl = new
>> MyContorl(emplo yeeid). However I need to load the control at runtime
>> so the have to call it this way LoadControl("My Control.ascx") and I
>> get an error that I have not supplied any parameter to the
>> constructor. Is there anyway around this? I guess I could change the
>> control so that I can insatiate it without supplying parameters and
>> assigning the properties later; but that doesn't seem like a very
>> clean solution. Thanks in advance.
>>[/color][/color]

[Hasani Blackwell]

Re: LoadControl() and Constructor Parameters

I think you're going to need a virtual Init[ializer] method and use that as
your 'constructor'. Though, to keep it flexible. I would make the method
signature
void Init[ializer](params object[] parameters). Just note that interfaces
are a collection virtual methods so you can do something like

puvlic Interface IBaseControl
{
void Initialize(para ms object[] parameters);
}

//then somehere in ur aspx code. but make sure this is done during the
Page_Init phase as because if you do this on say, Page_Load, the control
will execute all sequences to reach the same state as the caller (in this
case, Page_Load). It depends on what your intentions are and how the code
was written for the control though.

IBaseControl control = (IBaseControl) LoadControl("My Control.ascx").
control.Initial ize(employeeid) ;

or

public BaseControl
{
public virtual void Initialize(para ms object[] parameters);
}

//somewhere in aspx code.
BaseControl control = (BaseControl) LoadControl("My Control.ascx").
control.Initial ize(employeeid) ;


In the past, I never had a situation where a control or a page depended on a
non-default constructor to work. I've always used a system of, a well known
interface, or a class with virtual methods to expose methods (properties are
also methods) I needed to get the job done. And I disable session state and
other modules whenever I start a web project, I enable it as\when I need it
=]

And also, looking at your sample? code, you have the subcategory set in the
constructor, yet it does nothing, and you expose a get/set property that can
change the same field Why even have it in the constructor?!?! ?. You should
also make the _Subcategory a public field and rename it to Subcategory,
because it would be no different (other than the lines of code saved) than
adding the get/set property that modify _Subcategory.

"Sam Kuehn" <samkuehn@hotma il.com> wrote in message
news:1237616324 37123005255256@ msnews.microsof t.com...[color=blue]
>I didn't want to call any Session stuff in my control. I was hoping not to
>have to couple the control to this specific app that much. I would rather
>pass the value in. Although the value I pass in will probably come form
>the session object. Also all of the control in question do inherit from a
>base control. Just for further claification here is the full picure of
>what I am trying to do.
>
> //The Base Control
> namespace ExpenseReimburs ment.GUI.Contro ls.Add
> {
> public delegate void ItemAddedEventH andler(object sender, EventArgs ea);
> public class BaseControl : System.Web.UI.U serControl
> {
> // ToDo: Create constructor with params
> // public BaseControl(Sub CategoryEntity Subcategory)
> // {
> // _Subcategory = Subcategory;
> // }
> // private SubCategoryEnti ty _Subcategory;
> // public SubCategoryEnti ty Subcategory
> // {
> // get
> // {
> // return _Subcategory;
> // }
> // set
> // {
> // _Subcategory = value;
> // }
> // }
> #region Public Events
> public event ItemAddedEventH andler ItemAdded;
> protected virtual void OnItemAdded(Eve ntArgs ea)
> {
> if (ItemAdded != null)
> ItemAdded(this, ea);
> }
> #endregion
>
> #region Public Methods
> public void AddItem(Expense ReportDetailEnt ity lineItem)
> {
> lineItem.Save() ;
> OnItemAdded(new EventArgs());
> }
> public void AddItem(Expense ReportDetailCol lection lineItems)
> {
> lineItems.SaveM ulti();
> OnItemAdded(new EventArgs());
> }
> #endregion
>
> }
>
> }
>
> The actual control will depend on the type of expense they are adding for
> example:
>
> public class DefaultControl : BaseControl {} //the default control.
>
> And is called form the "Master Page" like this:
> private void LoadAddItemsCon trol(int Subcategoryid)
> {
> phAdd.Controls. Clear();
> SubCategoryEnti ty ojbSubCategoryE ntity = new
> SubCategoryEnti ty(Subcategoryi d);
> string control = "~/Controls/Add/Default.ascx";
> if (ojbSubCategory Entity.Inputcon trol.ToString() != "")
> control = "~/Controls/Add/" + ojbSubCategoryE ntity.Inputcont rol;
> GUI.Controls.Ad d.BaseControl ctlAddDetail =
> (GUI.Controls.A dd.BaseControl) LoadControl(con trol);
> ctlAddDetail.ID = "AddItem";
> //Add Event Handler
> ctlAddDetail.It emAdded += new
> GUI.Controls.Ad d.ItemAddedEven tHandler(this.I temAdded);
> //Add control
> phAdd.Controls. Add(ctlAddDetai l);
> }
>[color=green]
>> All ascxs have only 1 constructor. Maybe the class MyControl.ascx
>> inherits from has overloaded constructors, but the asp.net runtime
>> will call the default constructor. You're going to need to take a
>> different approach. If you want the control to know the employeeid,
>> use the session or something.
>>
>> "Sam Kuehn" <samkuehn@hotma il.com> wrote in message
>> news:1228796324 36423422339114@ msnews.microsof t.com...
>>[color=darkred]
>>> How do I accomplish the fallowing (is it even possible). Say I write
>>> a UserControl "MyControl.ascx ". Now I use
>>> LoadControl("My Control.ascx"). But I really want MyControl to require
>>> parameters in the constructor for example MyContorl oMyControl = new
>>> MyContorl(emplo yeeid). However I need to load the control at runtime
>>> so the have to call it this way LoadControl("My Control.ascx") and I
>>> get an error that I have not supplied any parameter to the
>>> constructor. Is there anyway around this? I guess I could change the
>>> control so that I can insatiate it without supplying parameters and
>>> assigning the properties later; but that doesn't seem like a very
>>> clean solution. Thanks in advance.
>>>[/color][/color]
>
>
>[/color]

[Sam Kuehn]

Re: LoadControl() and Constructor Parameters

I was hoping that I could require that a subcategory be set when the BaseControl
was instantiated (to help prevent errors and keep code clear). Right now
it is commented out for the reasons that I listed below (I get an error when
trying to instantiate a control based on this base control cause LoadControl()
was not passing parameters, subcategoryid, to the constructor). As far as
the getters and setters go: CodeRush creates them automatically and I am
just used to seeing things that way so I don't worry about changing it.
I guess if later on (will never happen) I could modify the private members
from within the class (again, I know in this situation it will never happen
but the code is already there so what the heck). Also, at some point, I
heard you should never have public variables, although the reason was never
really clear.
[color=blue]
> I think you're going to need a virtual Init[ializer] method and use
> that as
> your 'constructor'. Though, to keep it flexible. I would make the
> method
> signature
> void Init[ializer](params object[] parameters). Just note that
> interfaces
> are a collection virtual methods so you can do something like
> puvlic Interface IBaseControl
> {
> void Initialize(para ms object[] parameters);
> }
> //then somehere in ur aspx code. but make sure this is done during the
> Page_Init phase as because if you do this on say, Page_Load, the
> control will execute all sequences to reach the same state as the
> caller (in this case, Page_Load). It depends on what your intentions
> are and how the code was written for the control though.
>
> IBaseControl control = (IBaseControl) LoadControl("My Control.ascx").
> control.Initial ize(employeeid) ;
>
> or
>
> public BaseControl
> {
> public virtual void Initialize(para ms object[] parameters);
> }
> //somewhere in aspx code.
> BaseControl control = (BaseControl) LoadControl("My Control.ascx").
> control.Initial ize(employeeid) ;
> In the past, I never had a situation where a control or a page
> depended on a non-default constructor to work. I've always used a
> system of, a well known interface, or a class with virtual methods to
> expose methods (properties are also methods) I needed to get the job
> done. And I disable session state and other modules whenever I start a
> web project, I enable it as\when I need it =]
>
> And also, looking at your sample? code, you have the subcategory set
> in the constructor, yet it does nothing, and you expose a get/set
> property that can change the same field Why even have it in the
> constructor?!?! ?. You should also make the _Subcategory a public field
> and rename it to Subcategory, because it would be no different (other
> than the lines of code saved) than adding the get/set property that
> modify _Subcategory.
>
> "Sam Kuehn" <samkuehn@hotma il.com> wrote in message
> news:1237616324 37123005255256@ msnews.microsof t.com...
>[color=green]
>> I didn't want to call any Session stuff in my control. I was hoping
>> not to have to couple the control to this specific app that much. I
>> would rather pass the value in. Although the value I pass in will
>> probably come form the session object. Also all of the control in
>> question do inherit from a base control. Just for further
>> claification here is the full picure of what I am trying to do.
>>
>> //The Base Control
>> namespace ExpenseReimburs ment.GUI.Contro ls.Add
>> {
>> public delegate void ItemAddedEventH andler(object sender, EventArgs
>> ea);
>> public class BaseControl : System.Web.UI.U serControl
>> {
>> // ToDo: Create constructor with params
>> // public BaseControl(Sub CategoryEntity Subcategory)
>> // {
>> // _Subcategory = Subcategory;
>> // }
>> // private SubCategoryEnti ty _Subcategory;
>> // public SubCategoryEnti ty Subcategory
>> // {
>> // get
>> // {
>> // return _Subcategory;
>> // }
>> // set
>> // {
>> // _Subcategory = value;
>> // }
>> // }
>> #region Public Events
>> public event ItemAddedEventH andler ItemAdded;
>> protected virtual void OnItemAdded(Eve ntArgs ea)
>> {
>> if (ItemAdded != null)
>> ItemAdded(this, ea);
>> }
>> #endregion
>> #region Public Methods
>> public void AddItem(Expense ReportDetailEnt ity lineItem)
>> {
>> lineItem.Save() ;
>> OnItemAdded(new EventArgs());
>> }
>> public void AddItem(Expense ReportDetailCol lection lineItems)
>> {
>> lineItems.SaveM ulti();
>> OnItemAdded(new EventArgs());
>> }
>> #endregion
>> }
>>
>> }
>>
>> The actual control will depend on the type of expense they are adding
>> for example:
>>
>> public class DefaultControl : BaseControl {} //the default control.
>>
>> And is called form the "Master Page" like this:
>> private void LoadAddItemsCon trol(int Subcategoryid)
>> {
>> phAdd.Controls. Clear();
>> SubCategoryEnti ty ojbSubCategoryE ntity = new
>> SubCategoryEnti ty(Subcategoryi d);
>> string control = "~/Controls/Add/Default.ascx";
>> if (ojbSubCategory Entity.Inputcon trol.ToString() != "")
>> control = "~/Controls/Add/" + ojbSubCategoryE ntity.Inputcont rol;
>> GUI.Controls.Ad d.BaseControl ctlAddDetail =
>> (GUI.Controls.A dd.BaseControl) LoadControl(con trol);
>> ctlAddDetail.ID = "AddItem";
>> //Add Event Handler
>> ctlAddDetail.It emAdded += new
>> GUI.Controls.Ad d.ItemAddedEven tHandler(this.I temAdded);
>> //Add control
>> phAdd.Controls. Add(ctlAddDetai l);
>> }[color=darkred]
>>> All ascxs have only 1 constructor. Maybe the class MyControl.ascx
>>> inherits from has overloaded constructors, but the asp.net runtime
>>> will call the default constructor. You're going to need to take a
>>> different approach. If you want the control to know the employeeid,
>>> use the session or something.
>>>
>>> "Sam Kuehn" <samkuehn@hotma il.com> wrote in message
>>> news:1228796324 36423422339114@ msnews.microsof t.com...
>>>
>>>> How do I accomplish the fallowing (is it even possible). Say I
>>>> write a UserControl "MyControl.ascx ". Now I use
>>>> LoadControl("My Control.ascx"). But I really want MyControl to
>>>> require parameters in the constructor for example MyContorl
>>>> oMyControl = new MyContorl(emplo yeeid). However I need to load the
>>>> control at runtime so the have to call it this way
>>>> LoadControl("My Control.ascx") and I get an error that I have not
>>>> supplied any parameter to the constructor. Is there anyway around
>>>> this? I guess I could change the control so that I can insatiate
>>>> it without supplying parameters and assigning the properties later;
>>>> but that doesn't seem like a very clean solution. Thanks in
>>>> advance.
>>>>[/color][/color][/color]