FindControl in a gridview's dynamically-added template

  • Thread starter Thread starter Craig Buchanan
  • Start date Start date
C

Craig Buchanan

I dynamically add data-bound templates to a gridview in my ascx control.
while this works correctly when the gridview is databound to the
datatable, i'm having issues on postback.

i would like to iterate thru the gridview's rows, examine the databound
controls, then perform a database action. for some reason, i can't find
the controls.

i have a two templates: one that uses a label the other uses a textbox
to display data. when the InstantiateIn fires, i set the Id property
equal to 'Label_' + the name of the databound column, add the control
to the container and add the onDataBinding event handler.

what am i missing?

thanks,

Craig buchanan
 
Hi Craig
i would like to iterate thru the gridview's rows, examine the databound
controls, then perform a database action. for some reason, i can't find
the controls.
Click to expand...
Code :)
i have a two templates: one that uses a label the other uses a textbox
to display data. when the InstantiateIn fires, i set the Id property
equal to 'Label_' + the name of the databound column, add the control
to the container and add the onDataBinding event handler.
Click to expand...
Dito, show relevant Code to this issue.

How are you binding? On every Page_Load or with the IsPostBack-Constrain?
Where are you trying to access via .FindControl and how?
How are you put your dynamically names together "Label_"....?
 
Peter-

Thanks for the reply.

I bind the gridview in the Page_Load when it is not a postback.

I use a button's click event as a testing harness to examing the contents of
the gridview during a postback. In this event I loop thru the gridview's
rows, and attempt to find my textbox or label using findcontrol.

i dynamically create the templates prior to binding the data and in a
separate method. in the contructor of the template's InstantiateIn method,
i create the control (label or textbox) and assign its ID property to either
Label_[dataMember] or TextBox_[dataMember]. the [dataMember] value is
passed to the template in the constructor. moreover, the [dataMember]
values is used in the OnDataBinding event handler. pseudocode :

Class TextBoxTemplate
Implements ITemplate

private _dataMember as string
Public Sub New()
End Sub
Public Sub New(dataMember as string)
_dataMember=dataMember
End Sub

Public Sub InstantiateIn(container as )
dim tb as new TextBox
tb.Id = string.concat("Textbox_" ,_dataMember)

'add event handler (can't remember coding...)

container.Controls.Add(tb)

End Sub

public sub OnDataBinding(...)
'case sender as textbox
...
'cast sender's container as gridViewRow
...
'bind data (something similar)
tb.text = DataBinder.Eval(_dataMember)

end sub

End Class

i added logic to recreate the dynamic column in the Page_Init event, which
seemed to recreate the gridview correctly. i still can't seem to find my
dynamically-created controls in the gridview, however.

thoughts?

thanks a lot.

Craig
 
as your databind creates the dynamic controls, you need to rebind in the
postback before the onload event. the best place to create dynaic
control is in CreateChildControls method (which was designed for this).

-- bruce (sqlwork.com)

Craig said:
Peter-

Thanks for the reply.

I bind the gridview in the Page_Load when it is not a postback.

I use a button's click event as a testing harness to examing the contents of
the gridview during a postback. In this event I loop thru the gridview's
rows, and attempt to find my textbox or label using findcontrol.

i dynamically create the templates prior to binding the data and in a
separate method. in the contructor of the template's InstantiateIn method,
i create the control (label or textbox) and assign its ID property to either
Label_[dataMember] or TextBox_[dataMember]. the [dataMember] value is
passed to the template in the constructor. moreover, the [dataMember]
values is used in the OnDataBinding event handler. pseudocode :

Class TextBoxTemplate
Implements ITemplate

private _dataMember as string
Public Sub New()
End Sub
Public Sub New(dataMember as string)
_dataMember=dataMember
End Sub

Public Sub InstantiateIn(container as )
dim tb as new TextBox
tb.Id = string.concat("Textbox_" ,_dataMember)

'add event handler (can't remember coding...)

container.Controls.Add(tb)

End Sub

public sub OnDataBinding(...)
'case sender as textbox
...
'cast sender's container as gridViewRow
...
'bind data (something similar)
tb.text = DataBinder.Eval(_dataMember)

end sub

End Class

i added logic to recreate the dynamic column in the Page_Init event, which
seemed to recreate the gridview correctly. i still can't seem to find my
dynamically-created controls in the gridview, however.

thoughts?

thanks a lot.

Craig

Peter Bucher said:
Hi Craig

Code :)

Dito, show relevant Code to this issue.

How are you binding? On every Page_Load or with the IsPostBack-Constrain?
Where are you trying to access via .FindControl and how?
How are you put your dynamically names together "Label_"....?

--
Gruss, Peter Bucher
Microsoft MVP - Visual Developer ASP / ASP.NET, Switzerland
http://www.aspnetzone.de/ - ASP.NET Zone, die ASP.NET Community
http://www.aspnetzone.de/blogs/peterbucher/ - Auf den Spuren von .NET
Click to expand...
Click to expand...
 
bruce-

i'm trying to pivot data in code, while two columns are available at
design time, the other column (based on a date column) are dynamically
generated.

my approach has been such:

when Not Ispostback

1). pivot the detailed datatable into a dynamically-created pivoted
datatable. for example, i am given:
ET FS DT $
-- -- -- -
A A 2008 50
A B 2008 200
A B 2009 100

this is pivoted to:

ET FS 2008 2009
-- -- ---- ----
A A 50
A B 200 100

2). add dynamically-created template columns (4 in this example) to the
datagrid based on the columns in the pivoted datatable. these template
columns are stored in the viewstate.

3). bind gridview to pivoted datatable

during a postback

1). retrieve the template columns from the viewstate
2). add them to the gridview
3). allow gridview to restore data

from what i've read, i need to add the template columns to the gridview
in the Page_Init event, but the template columns, contained in the
viewstate, aren't available until the Page_Load event.

is there another way to handle this?

thanks.

bruce said:
as your databind creates the dynamic controls, you need to rebind in the
postback before the onload event. the best place to create dynaic
control is in CreateChildControls method (which was designed for this).

-- bruce (sqlwork.com)

Craig said:
Peter-

Thanks for the reply.

I bind the gridview in the Page_Load when it is not a postback.

I use a button's click event as a testing harness to examing the
contents of the gridview during a postback. In this event I loop thru
the gridview's rows, and attempt to find my textbox or label using
findcontrol.

i dynamically create the templates prior to binding the data and in a
separate method. in the contructor of the template's InstantiateIn
method, i create the control (label or textbox) and assign its ID
property to either Label_[dataMember] or TextBox_[dataMember]. the
[dataMember] value is passed to the template in the constructor.
moreover, the [dataMember] values is used in the OnDataBinding event
handler. pseudocode :

Class TextBoxTemplate
Implements ITemplate

private _dataMember as string
Public Sub New()
End Sub
Public Sub New(dataMember as string)
_dataMember=dataMember
End Sub

Public Sub InstantiateIn(container as )
dim tb as new TextBox
tb.Id = string.concat("Textbox_" ,_dataMember)

'add event handler (can't remember coding...)

container.Controls.Add(tb)

End Sub

public sub OnDataBinding(...)
'case sender as textbox
...
'cast sender's container as gridViewRow
...
'bind data (something similar)
tb.text = DataBinder.Eval(_dataMember)

end sub

End Class

i added logic to recreate the dynamic column in the Page_Init event,
which seemed to recreate the gridview correctly. i still can't seem
to find my dynamically-created controls in the gridview, however.

thoughts?

thanks a lot.

Craig

Peter Bucher said:
Hi Craig

i would like to iterate thru the gridview's rows, examine the
databound controls, then perform a database action. for some
reason, i can't find the controls.
Code :)

i have a two templates: one that uses a label the other uses a
textbox to display data. when the InstantiateIn fires, i set the Id
property equal to 'Label_' + the name of the databound column, add
the control to the container and add the onDataBinding event handler.
Dito, show relevant Code to this issue.

How are you binding? On every Page_Load or with the
IsPostBack-Constrain?
Where are you trying to access via .FindControl and how?
How are you put your dynamically names together "Label_"....?

--
Gruss, Peter Bucher
Microsoft MVP - Visual Developer ASP / ASP.NET, Switzerland
http://www.aspnetzone.de/ - ASP.NET Zone, die ASP.NET Community
http://www.aspnetzone.de/blogs/peterbucher/ - Auf den Spuren von .NET
Click to expand...
Click to expand...
Click to expand...
 
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