Dynamically added user control

[Chris]

I am dynamically adding a user control to each row in a gridview. The reason
I am doing it dynamically is the user control is different depending on
certain data in the gridview. The gridview contains a placeholder and I add
the control to it, the user control is a formview bound to an object
datsource. This works great until I post back the page and the user control
disappears. What am I doing wrong? Regards, Chris.



Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As
System.Web.UI.WebControls.GridViewRowEventArgs) Handles
GridView1.RowDataBound

If e.Row.RowType = DataControlRowType.DataRow Then

Dim o As ObjectDataSource = CType(e.Row.FindControl("objdsgetorders"),
ObjectDataSource)

o.SelectParameters(0).DefaultValue =
GridView1.DataKeys(e.Row.DataItemIndex).Value

Dim pl As PlaceHolder = CType(e.Row.FindControl("plchildgw"), PlaceHolder)

Dim ctl As Control = LoadControl("updateorder.ascx")

Dim odssub As ObjectDataSource = CType(ctl.FindControl("odscustomer"),
ObjectDataSource)

odssub.SelectParameters("customerid").DefaultValue =
CInt(GridView1.DataKeys(e.Row.DataItemIndex).Value)

pl.Controls.Add(ctl)

End If

End Sub

 

[Eliyahu Goldin]

You have to re-create dynamically added controls on every postback,
preferably in Page_Init event. It could be easier to cater for all possible
controls in the ItemTemplate and show/hide them as required with css rule
display:none.

--
Eliyahu Goldin,
Software Developer & Consultant
Microsoft MVP [ASP.NET]
http://msmvps.com/blogs/egoldin
http://usableasp.net

 

[Chris]

I kind of like the user control idea as it is a little more modular. I am
going to end end with about 20 variations of user control, doing it in the
item template seem more complex. How would I go about adding the user
controls to a gridview from the page init event. Regards, Chris.

You have to re-create dynamically added controls on every postback,
preferably in Page_Init event. It could be easier to cater for all
possible controls in the ItemTemplate and show/hide them as required with
css rule display:none.

--
Eliyahu Goldin,
Software Developer & Consultant
Microsoft MVP [ASP.NET]
http://msmvps.com/blogs/egoldin
http://usableasp.net

I am dynamically adding a user control to each row in a gridview. The
reason I am doing it dynamically is the user control is different
depending on certain data in the gridview. The gridview contains a
placeholder and I add the control to it, the user control is a formview
bound to an object datsource. This works great until I post back the page
and the user control disappears. What am I doing wrong? Regards, Chris.



Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As
System.Web.UI.WebControls.GridViewRowEventArgs) Handles
GridView1.RowDataBound

If e.Row.RowType = DataControlRowType.DataRow Then

Dim o As ObjectDataSource = CType(e.Row.FindControl("objdsgetorders"),
ObjectDataSource)

o.SelectParameters(0).DefaultValue =
GridView1.DataKeys(e.Row.DataItemIndex).Value

Dim pl As PlaceHolder = CType(e.Row.FindControl("plchildgw"),
PlaceHolder)

Dim ctl As Control = LoadControl("updateorder.ascx")

Dim odssub As ObjectDataSource = CType(ctl.FindControl("odscustomer"),
ObjectDataSource)

odssub.SelectParameters("customerid").DefaultValue =
CInt(GridView1.DataKeys(e.Row.DataItemIndex).Value)

pl.Controls.Add(ctl)

End If

End Sub

 

[Mark Rae]

I kind of like the user control idea as it is a little more modular. I am
going to end end with about 20 variations of user control, doing it in the
item template seem more complex. How would I go about adding the user
controls to a gridview from the page init event.

Eliyahu is right, though I think you have slightly misunderstood his
advice...

Dynamically created controls need to be dynamically created every time the
page loads - they don not persist across a postback.

However, you don't add the dynamically created controls to the GridView in
Page_Init - you simply create them there and hide them for use later.

Although dynamic controls *can* be created anywhere in code-behind, they
have a tendency not to work properly if they are created any later in the
page cycle than Page_Init - specifically, their events don't get wired up
successfully.

Thus, when you come to bind your GridView, you can use its OnDataBinding
event simply to add the dynamically created controls to the GridView as
required...

 

[Chris]

I need help, I've looking at this for too long. I need to add the controls
on every postback but when I load the control in the init and add it on
databinding it still disappears on postback. I've been having more success
with adding the controls on the page load.

For Each row In GridView1.Rows

Dim pl As PlaceHolder = CType(row.FindControl("plchildgw"), PlaceHolder)

pl.Controls.Add(mastercontrol)

Next

but the control only binds to the last element in the gridview, which may be
some thing stupid I have done. Thanks for the help

Here is the code where I try to bind later

Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs)
Handles Me.Init

mastercontrol = LoadControl("updateorder.ascx")

End Sub

Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As
System.Web.UI.WebControls.GridViewRowEventArgs) Handles
GridView1.RowDataBound

If e.Row.RowType = DataControlRowType.DataRow Then

Dim o As ObjectDataSource = CType(e.Row.FindControl("objdsgetorders"),
ObjectDataSource)

o.SelectParameters(0).DefaultValue =
GridView1.DataKeys(e.Row.DataItemIndex).Value

Dim pl As PlaceHolder = CType(e.Row.FindControl("plchildgw"), PlaceHolder)

Dim odssub As ObjectDataSource =
CType(mastercontrol.FindControl("odscustomer"), ObjectDataSource)

odssub.SelectParameters("customerid").DefaultValue =
CInt(GridView1.DataKeys(e.Row.DataItemIndex).Value)

pl.Controls.Add(mastercontrol)

End If

End Sub

 

[Mark Rae]

Here is the code where I try to bind later

Protected Sub Page_Init(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Init

mastercontrol = LoadControl("updateorder.ascx")

End Sub

That creates *one* dynamic control.

but the control only binds to the last element in the gridview, which may
be some thing stupid I have done.

You need as many dynamic controls as there are rows in the GridView...

 

[Chris]

I've got it working with this. It makes sense to me but if you can see
potential problems.....

Dim row As GridViewRow

Dim i As Integer = 0

For Each row In GridView1.Rows

Dim txt As New TextBox()

Dim control As New Control()

mastercontrol = LoadControl("updateorder.ascx")

Dim odssub As ObjectDataSource =
CType(mastercontrol.FindControl("odscustomer"), ObjectDataSource)

odssub.SelectParameters("customerid").DefaultValue =
GridView1.DataKeys(row.RowIndex).Value

Dim pl As PlaceHolder = CType(row.FindControl("plchildgw"), PlaceHolder)

pl.Controls.Add(mastercontrol)

Next

 

[Mark Rae]

Dim txt As New TextBox()
Dim control As New Control()

What are those two variables for...? You don't appear to be using them
anywhere...

 

[Chris]

They've been left in by accident

What are those two variables for...? You don't appear to be using them
anywhere...

 

[Mark Rae]

They've been left in by accident

Ah...