TemplateBuilder

[Jerry C]

I am trying to use the template builder in a Web part. this code runs but no
control in the Template column. this is the CreateChildControls Sub from Form
4 of a sample from MSDN "Introducing the ASP.NET 2.0 Web Parts Fromework"
modifyed to try to add a grid view and custom columns to the control. The
grid shows ok and there is data in it and the bound field and Connand field
is OK.

This is the code.

Protected Overrides Sub CreateChildControls()
'Create the GridView
Controls.Clear()
grdTree = New GridView
grdTree.AutoGenerateColumns = True
grdTree.EmptyDataText = "There is no data today"
grdTree.ID = "gvTree"
grdTree.Attributes.Add("runat", "server")
grdTree.Width = 100%

'Try the TemplateField field is created and the header Text is OK
'but there is no DropDownList box in the field.

Dim grdTF As New TemplateField
grdTF.HeaderText = "Checkbox Template Field"
Dim ddlBox As New DropDownList
ddlBox.ID = "ddltop"
ddlBox.Visible = True
ddlBox.Items.Add("One")
ddlBox.Items.Add("Two")
Dim CT As New Control
CT.Controls.Add(ddlBox)
Dim grdTB As New TemplateBuilder
grdTF.ItemTemplate = grdTB
grdTF.ItemTemplate.InstantiateIn(CT)
grdTree.Columns.Add(grdTF)

'CommandField works OK.
Dim grdCF As CommandField = New CommandField
grdCF.ShowSelectButton = True
grdTree.Columns.Add(grdCF)

'BoundField works OK.
Dim grdBF As BoundField = New BoundField
grdBF.DataField = "ProductID"
grdTree.Columns.Add(grdBF)

Dim productTable As New DataTable()
Dim dad As New SqlDataAdapter(selectString, _
connectionString)
dad.Fill(productTable)
grdTree.DataSource = productTable
grdTree.DataBind()
Me.Controls.Add(grdTree)

End Sub

Thank you,

 

[Steven Cheng[MSFT]]

Hello Jerry,

From your description, I got that you're developing a custom
TemplateBuilder for GridView and the GridView and templatebuilder(template)
will be creaetd programmatically in your web part's control constructing
code, correct?

Based on the code fragment you provided, I found that you manually call the
TemplateBuilder.InstantiateIn method and pass child controls into it.
Actually, this method is designed to be invoke by ASP.NET runtime rather
than ourself. For your scenario, you want to create a custom Templateclass
for GridView TemplateField, you can considier the following options:

1. Create a custom class which implements the ITemplate interface, and
override the InstantiateIn method, put the child control constructing code
in it. For example:

==============================
Public Class DropdownTemplate
Implements ITemplate


Public Sub InstantiateIn(ByVal container As System.Web.UI.Control)
Implements System.Web.UI.ITemplate.InstantiateIn

Dim ddlBox As New DropDownList
ddlBox.ID = "ddltop"
ddlBox.Visible = True
ddlBox.Items.Add("One")
ddlBox.Items.Add("Two")

container.Controls.Add(ddlBox)

End Sub
End Class
==================================================


Then, in the page, you can use the following code to construct this custom
Template and assign it to TemplateField's ItemTemplate:

===========
Dim tf1 As New TemplateField

tf1.HeaderText = "Custom Template"
tf1.ItemTemplate = New DropdownTemplate()

grid.Columns.Add(tf1)
===================



2. Create a whole custom GridView Field which dervied from
"DataControlField" class. e.g

===============================
Public Class MyDropdownField
Inherits DataControlField


Protected Overrides Function CreateField() As
System.Web.UI.WebControls.DataControlField

Return New MyDropdownField

End Function

Public Overrides Sub InitializeCell(ByVal cell As
System.Web.UI.WebControls.DataControlFieldCell, ByVal cellType As
System.Web.UI.WebControls.DataControlCellType, ByVal rowState As
System.Web.UI.WebControls.DataControlRowState, ByVal rowIndex As Integer)

Select Case cellType
Case DataControlCellType.Header

cell.Text = Me.HeaderText

Case DataControlCellType.Footer

Case DataControlCellType.DataCell

If rowState = DataControlRowState.Normal Or rowState =
DataControlRowState.Alternate Then

Dim ddlBox As New DropDownList
ddlBox.ID = "ddltop"
ddlBox.Visible = True
ddlBox.Items.Add("One")
ddlBox.Items.Add("Two")

cell.Controls.Add(ddlBox)
End If


End Select


End Sub
End Class
========================================


Then, we can simply construct and add this class's instance into GridView's
columns collection. e.g.

===============
Dim tf2 As New MyDropdownField
tf2.HeaderText = "My Custom TemplateField"

grid.Columns.Add(tf2)

=======================


In addition, there are some other ways to create custom template (such as
load from usercontrol) in asp.net. see below:

http://msdn.microsoft.com/msdnmag/issues/05/06/CuttingEdge/default.aspx

And here is another article describing hwo to create a custom template
column. Though it is writen for ASP.NET 1.1 datagrid, it also applies to
GridView

#Creating Custom Columns for the ASP.NET Datagrid
http://msdn.microsoft.com/library/en-us/dnaspp/html/creatingcustomcolumns.as
p?frame=true


Please feel free to let me know if you have any other questions or concerns.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead



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