I'm inheriting a DropDownList to add two custom ListItems. The first item is "Select one..." and the second item gets added at the end, it's value is "Custom".
I override DataBind and use the following code:
Dim data As List(Of ListItem) = CType(DataSource, List(Of ListItem))
data.Insert(0, New ListItem("Select one...", SelectOneListItemValue))
If DisplayCustomOption Then
data.Insert(data.Count, New ListItem("Custom", CustomListItemValue))
End If
DataSource = data
MyBase.DataBind()
The problem is this code won't work if the DataSource is anything other than a List of ListItem. Is there a better way of doing this?
You could make the assumption that the data source always inherits IList, in which case you could do the following:
Dim data As IList = CType(DataSource, IList)
data.Insert(0, New ListItem("Select one...", SelectOneListItemValue))
' And so on...
Of course, this assumes that whatever the data source is, it allows you to add objects of the type ListItem. But this might be generic enough for what you need.
You could just leave the databind alone and add your special Items in the DataBound event handler.
Protected Sub MyDropDownList_DataBound(sender As Object, e As EventArgs) _
Handles MyDropDownList.DataBound
MyBase.Items.Insert(0, New ListItem("Select One...", SelectOneListItemValue))
If DisplayCustomOption Then
MyBase.Add(New ListItem("Custom", Custom))
End If
End Sub
(My VB.NET is limited, so you may need to adjust syntax)
Related
I'm using a custom template class to generate lines with my repeater control, i'd like to be able to specify the controls in this repeater dynamically from the code behind my aspx page.
In the code behind I've added controls to a list like this:
Dim lstControls As New List(Of Control)
lstControls.Add(New TextBox)
lstControls.Add(New Label)
lstControls.Add(New CheckBox)
lstControls.Add(New DropDownList)
lstControls.Add(New CheckBox)
Then i use this line to add the controls to my template
rptrSummary.ItemTemplate = New myTemplate(ListItemType.Item, , lstControls)
From the instantiateIn sub i'm doing something like this:
Dim ph As New PlaceHolder
For i = 0 To lstControls.Count - 1
ph.Controls.Add(lstControls(i))
Next
This doesn't work properly and following .databind() of my repeater control the controls i specify only appear on the final row. I think this is because i've only declared the controls as NEW once, so i only have one rows worth.
tldr?/ conclusion:
How can i generate new controls of the same type as controls from my list? Something like:
Dim newControl as new Control = type(lstControl(0))
(this obviously doesn't work)
I've found the answer, here are some examples in case anyone else is stuck (i may also change the title so it's more similar to likely search criteria):
dim egTextbox as new textbox
dim egLabel as new label
dim newObject1 as Object = Activator.CreateInstance(egTextbox.GetType)
dim newObject2 as Object = Activator.CreateInstance(egLabel.GetType)
newObject1 is now a textbox
newObject2 is now a label
I'm trying to develop a custom GridView control with properties OpenFormModal and ModalWindowWidth and ModalWindowHeight and a few more.
From CustomGridView class I call an instance of CustomGVITemplate:
Protected Overrides Function CreateColumns(ByVal dataSource As PagedDataSource, ByVal useDataSource As Boolean) As ICollection
Dim columnList As ICollection = MyBase.CreateColumns(dataSource, useDataSource)
Dim cmdDel As New TemplateField
cmdDel.ItemTemplate = New CustomGVITemplate(ListItemType.Item, "delete")
'I CAN'T ASSING VALUE TO CUSTOM PROPERTIES HERE
list.Add(cmdDel)
End Function
The thing is, I should access CustomGridView properties from within InstantiateIn sub inside CustomGVITemplate class, the only way I know to do it is pass these parameters through
New CustomGVITemplate(ListItemType.Item, "delete", ALL-OTHER-PROPERTIES-HERE)
I don't like this solution as I'm forced to do a lot of Optional parameters so not all calls use all properties, also, I can't find the way to define properties in CustomGVITemplate and asign values to them.
Other possible solutions?
Thank you
SOLVED: The thing was I was trying to access values and proerties in CreateColumns event, when data hasn't been binded yet, the solution was to create CommandButton (or Button) in CreateColumns events and access properties and DataKeys later, in RowCommand or button OnClick events.
I inherited a site which I am in the middle of updating which has a DropDownList and a RangeValidator assigned to it. The data is bound to the dropdown on Page_Load. The values are retrieved from the database so the value property of each item is set to the unique ID of the item in the DB.
The RangeValidator looks something like:
<asp:rangevalidator id="ddRangeValidator" runat="server" ControlToValidate="ddMenu" ErrorMessage="Please select value in range" MinimumValue="1" MaximumValue="100000" Type="Integer">*</asp:rangevalidator>
I have a method which automatically populates this value in jQuery e.g.
$("#ddMenu").val("An Option");
This works, however, when I try to post the page the range validation fails. Then even if I manually select that value, or select another valid value it still won't validate. The only way to make it validate is to select non-valid value and then re-selecting a valid one.
Any ideas?
Update
Here is the data binding code:
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load, Me.Load
If Not Page.IsPostBack Then
Dim ds As New DataSet()
Dim myDbObject As New myDbObject()
ds = myDbObject.ToDataSet() // retrieves all objects from the database
// store the results in a temporary view to filter
Dim dv As DataView
dv = New DataView(ds.Tables(0), "IsLive = True", "ID", DataViewRowState.CurrentRows)
Dim i As Integer = 0
ddMenu.Items.Add("Select a value")
ddMenu.Items.Item(0).Value = 0
// add all objects from filtered list into drop down menu
For i = 0 To dv.Count - 1
With ddMenu.Items
// add a new item
.Add(dv.Item(i).Item("Name"))
// set the Value property as unique ID of object
.Item(i + 1).Value = dv.Item(i).Item("ID")
End With
Next
End If
End If
Turns out it was an issue with my page loading twice...so now the issue is going to be tracking down why it is loading twice!
I guess the Range validator verifies the actual "value" of the dropdown list. May it be possible that by using jQuery to populate your dropdown the actual entry doesn't get a proper option "value"? Could you maybe post the rendered HTML code of your dropdown list?
i have few texboxt and dropdownlist, which their id would be something like "txtName1, txtName2, txtName3..." and "ddlAction1, ddlAction2, ddlAction3...."! I would to to dynamically set the textboxt and dropdownlist id into something like this:
for i as integer = 0 to 6
a = txtName+i.text
b = ddlAction+i.SelectedValue
next i
Need help from you guys to do this! thanks....
The key is FindControl, which looks up a control by its expected ID:
For i As Integer = 0 To 5
Dim txt As TextBox = TryCast(Me.Page.FindControl("txtName" & i.ToString()), TextBox)
Dim ddl As DropDownList = TryCast(Me.Page.FindControl("ddlAction" & i.ToString()), DropDownList)
If txt IsNot Nothing AndAlso ddl IsNot Nothing Then
Dim a As String = txt.Text
Dim b As String = ddl.SelectedValue
End If
Next
It will return null/nothing if a control with that ID isn't found.
Note that FindControl will only search the given control's (or Page's) immediate children, not the entire control tree. To search recursively, you need to use your own FindControl method.
Private Function FindControlRecursive(ByVal control As Control, ByVal id As String) As Control
Dim returnControl As Control = control.FindControl(id)
If returnControl Is Nothing Then
For Each child As Control In control.Controls
returnControl = child.FindControlRecursive(id)
If returnControl IsNot Nothing AndAlso returnControl.ID = id Then
Return returnControl
End If
Next
End If
Return returnControl
End Function
.Net requires you to resolve your variable names at compile time, rather than runtime like your code is trying to do. This is a good thing, as it prevents you from making certain kinds of errors. But it does mean you'll need to look at an alternative approach for this particular problem.
One option is a FindControl -based method. But odds are the controls you care about are grouped together on the page. If they aren't already, put them in a common container control, like a panel. Then you can do something like this (requires System.Linq):
For Each t As TextBox In MyContainer.Controls.OfType(Of TextBox)()
a = t.Text
Next t
For Each d As DropDownList In MyContainer.Controls.OfType(Of DropDownList)()
b = d.SelectedValue
Next d
Also, I hope you're really doing something other than assignment inside your loop. Otherwise, most of the work is for nothing as you will exit the loop having simply assigned the value from the last iteration to your variable.
Finally, it seems like these controls might work in pairs. To me, that's a situation that calls out for you to implement a user control.
I'm not a webforms expert, but I believe the page stores a reference to each control present in the page.
You can think of webforms like an n-ary tree... each control has a parent and can have 0 to many children. So, if these are static controls you should just be able to grab a reference to their parent and iterate over that... with no need for the children's ids.
Also, you can query for children based on their id... something like myControl["myID1"] so you can concat the number with the string and get the control that way.
Lastly, if these are purely dynamic controls, i.e. you don't know how many there are, just store references to them in an ordered collection and iterate over them that way.
EDIT:
Here we go:
WebControl myControl;
myControl.Controls.Add(someControlReference);
Then, to grab a control by ID:
WebControl someControl = myControl.FindControl("someControlID1");
From there you can do like:
string a = someControl.Text
I am trying to create a more detailed item template for the standard CheckBoxList control. It exposes an ITemplate property called TemplateControl but I wasn't able to find a straightforward resource on how to actually use it. Here's the code I have so far:
Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
MyBase.OnLoad(e)
Dim items As New List(Of ListItem)
items.Add(New ListItem() With {.Text = "A", .Value = "1"})
items.Add(New ListItem() With {.Text = "B", .Value = "2"})
items.Add(New ListItem() With {.Text = "C", .Value = "3"})
Dim lst As New CheckBoxList()
Dim tpl As ITemplate = LoadTemplate("~/CustomListItem.ascx")
Dim g As New TemplateControlWrapper()
tpl.InstantiateIn(g)
lst.TemplateControl = g
lst.DataSource = items
lst.DataBind()
Form.Controls.Add(lst)
End Sub
Class TemplateControlWrapper
Inherits UserControl
End Class
It seems to be ignoring the TemplateControl property completely. Any ideas?
CheckBoxList's TemplateControl property does not actually allow you to modify the template of the CheckBoxList. This is a property inherited all the way from System.Web.UI.Control, and it means the templated control that the CheckBoxList lives in, or put another way, the .aspx page, .ascx user control, or master page that the control lives on. (If the control is included as part of a composite control, I honestly don't know without experimenting if the TemplateControl property would return null, or keep going up the control chain until it found a Page or UserControl.)
The CheckBoxList control does not offer the kind of template modification you are looking to do. You may need to custom-bind a Repeater or DataList (with a CheckBox control in the ItemTemplate) in order to achieve the functionality you're looking for.
You are missing a couple things... this MSDN page has a pretty straightforward example:
http://msdn.microsoft.com/en-us/library/36574bf6.aspx
For starters, you are missing INamingContainer.