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.
Related
I'm working with a website written in aspx.net over vb.
I have a placeHolder, and I create a table of names inside this PlaceHolder, each name has an HtmlInputCheckBox next to it.
Im doing this in the aspx.vb file, when the page is uploading.
Then, when the user wants to send mail, he presses a button and than I need to access the checkboxes, and I'm having problems with this, the Sub doesn't know the checkBox object.
I would love for some help,
Thank you!
I understand that you're creating those checkboxes dynamically?
In such case, store them as global member of the class, most simple way is to have List of them:
List<HtmlInputCheckBox> arrCheckboxes = new List<HtmlInputCheckBox>();
...
...
HtmlInputCheckBox myCheckbox = new HtmlInputCheckBox();
arrCheckboxes.Add(myCheckbox);
...
This is C# but should be easy to translate to VB - anyhow having this, you can access the List and it should work.
Worst case as "last resort" you can simply iterate the whole Request.Form collection and look for Keys with name matching to the checkbox name.
Put this in the procedure...
Dim chkValue1 As New CheckBox
Dim chkValue2 As New CheckBox
'Find the Checkbox Controls in the PlaceHolder and cast them to the checkboxes we just made.
chkValue1 = CType(YourPlaceHolder.FindControl("Checkbox1ControlId"), CheckBox)
chkValue2 = CType(YourPlaceHolder.FindControl("Checkbox2ControlId"), CheckBox)
'Now you can do this...
Dim bolIsValue1Checked As Boolean = chkValue1.Checked
If I have a master 'composite custom server control', with several child custom controls, is it possible, for the master control to share its viewstate with the child controls, which are also custom composite server controls,(all of the controls are composite custom server controls)?
To expand a little more, say I have a Person control, Address control, Phone control and Notes control. Address, Phone and Notes can exist as either independant controls, or as part of the Person control. Since each control is responsible for its own viewstate, and stores required data in it, so it can render/postback etc, it ends up that there is a lage duplication in the viewstate, since the Person control stores all the data, and then each child control stores its own data again. Also, to further complicate things, the Person Control adds the child controls dynamically, so its possible to add a 2nd address/phone number/note etc,which can cause yet a larger viewstate(up to 1MB).
In the case of when all the Address/Phone/etc controls are children of the the Person Control, is it possible for me to somehow share common viewstate data, so I dont have 2/3/4 copies of some stuff in the viewstate, and when they are not components, just act as normal?
I do have one idea for a solution, but its fairly nasty imo, where I could modify the Person control, expose its viewstate or the data, and then in the child control, would check the control hierarchy, and if the child control is part of a Person, dont use to its own viewstate, use the exposed one. This would require me to rework alot of the existing code, which I'd rather avoid if possible.
The first question I'd ask is, "How much of this data do you really need to keep on the ViewState?" For example, is there enough information in a typical page request to be able to rebuild all of the information that is in some of these controls?
I find that ASP.NET typically uses ViewState far more than I really need it to, and if you're getting a 1MB viewstate, I suspect the same is probably true for you. I highly recommend reading this article to get a more full understanding of how ViewState works, what causes values to get saved to ViewState, and how to avoid using it where it's not necessary. You may be able to solve the bulk of your problem simply by doing more of your work in Page_Init instead of Page_Load, for example.
You can "share" a ViewState between any number of objects by passing it around as a StateBag type, or by using delegate functions that return the ViewState that needs to be shared. The usage of this, however; should be limited to very specific circumstances, because typically controls use Properties to expose their ViewState data to other objects (See the link #StriplingWarrior posted here). That being said, here is some example code:
User Control: SharedState.ascx
<%# Control Language="vb" AutoEventWireup="false" CodeBehind="SharedState.ascx.vb" Inherits="TestSite.SharedState" %>
User Control: SharedState.ascx.vb
Public Class SharedState
Inherits System.Web.UI.UserControl
Public Delegate Function GetStateDelegate() As StateBag
Public Const SharedValueKey = "The key used to access the ViewState dictionary"
Public Property GetState() As GetStateDelegate
' Different ways to get values
Public Function GetTypedValue(Of TValue)() As TValue
Return CTypeDynamic(GetValue(), GetType(TValue))
End Function
Public Function GetValue() As Object
' Use the delegate to get the view state from the parent
Return GetState.Invoke()(SharedValueKey)
End Function
Public Function GetValue(state As StateBag) As Object
Return state(SharedValueKey)
End Function
' Different ways to set values
Public Sub SetTypedValue(Of TValue)(value As TValue)
Me.SetValue(value)
End Sub
Public Sub SetValue(value As Object)
GetState.Invoke()(SharedValueKey) = value
End Sub
Public Sub SetValue(state As StateBag, value As Object)
state(SharedValueKey) = value
End Sub
' Set ViewState value using a key and the delegate
Public Sub SetStateWithKey(key As String, value As Object)
GetState.Invoke()(key) = value
End Sub
' Get ViewState value using a key and the delegate
Public Function GetStateWithKey(key As String) As Object
Return GetState.Invoke()(key)
End Function
End Class
Page: SharedStatePage.aspx
<%# Page Language="vb" AutoEventWireup="false" CodeBehind="SharedStatePage.aspx.vb" Inherits="TestSite.SharedStatePage" %>
<%# Register src="SharedState.ascx" tagname="SharedState" tagprefix="uc1" %>
<uc1:SharedState ID="SharedState1" runat="server" />
<uc1:SharedState ID="SharedState2" runat="server" />
Page: SharedStatePage.aspx.vb
Public Class SharedStatePage
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
' Set up SharedState 1 & 2 to use the delegate '
SharedState1.GetState = AddressOf GetState
SharedState2.GetState = AddressOf GetState
' Set the view state from the page '
ViewState(SharedState.SharedValueKey) = 23
' Read the view state from the user controls '
Dim sharedInt As Integer
sharedInt = SharedState1.GetTypedValue(Of Integer)()
sharedInt = SharedState1.GetValue()
sharedInt = SharedState1.GetValue(ViewState)
sharedInt = SharedState2.GetValue()
' Set the view state from one of the user controls '
SharedState2.SetTypedValue(Of String)("Hello")
Dim sharedStr As String = ViewState(SharedState.SharedValueKey)
sharedStr = SharedState1.GetTypedValue(Of String)()
sharedStr = SharedState2.GetValue()
' Use a different key to set and get view state data '
ViewState("MyKey") = New With {.Name = "Some Object", .Value = 46}
Dim myObj = SharedState1.GetStateWithKey("MyKey")
SharedState2.SetStateWithKey("MyKey", "New Value")
myObj = ViewState("MyKey")
End Sub
Private Function GetState() As StateBag
Return ViewState
End Function
End Class
Use with caution, or don't use with abandon.
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.
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)
In ASP.NET, if I databind a gridview with a array of objects lets say , how can I retrieve and use foo(index) when the user selects the row?
i.e.
dim fooArr() as foo;
gv1.datasource = fooArr;
gv1.databind();
On Row Select
Private Sub gv1_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles gv1.RowCommand
If e.CommandName = "Select" Then
'get and use foo(index)
End If
End Sub
If you can be sure the order of items in your data source has not changed, you can use the CommandArgument property of the CommandEventArgs.
A more robust method, however,is to use the DataKeys/SelectedDataKey properties of the GridView. The only caveat is that your command must be of type "Select" (so, by default RowCommand will not have access to the DataKey).
Assuming you have some uniqueness in the entities comprising your list, you can set one or more key property names in the GridView's DataKeys property. When the selected item in the GridView is set, you can retrieve your key value(s) and locate the item in your bound list. This method gets you out of the problem of having the ordinal position in the GridView not matching the ordinal position of your element in the data source.
Example:
<asp:GridView ID="GridView1" runat="server" AutoGenerateSelectButton="True"
DataKeyNames="Name" onrowcommand="GridView1_RowCommand1"
onselectedindexchanged="GridView1_SelectedIndexChanged">
</asp:GridView>
Then the code-behind (or inline) for the Page would be something like:
protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
{
// Value is the Name property of the selected row's bound object.
string foo = GridView1.SelectedDataKey.Value as string;
}
Another choice would be to go spelunking in the Rows collection of the GridView, fetching values a column at a time by getting control values, but that's not recommended unless you have to.
Hope this helps.
in theory the index of the row, should be the index of foo (maybe +1 for header row, you'll need to test). so, you should be able to do something along these lines
dim x as object = foo(e.row.selectedIndex)
The other alternative is to find a way to databind the index to the commandArgument attribute of the button.
There's probably a cleaner way of doing this, but you could set the CommandArgument property of the row to its index. Then something like foo(CInt(e.CommandArgument)) would do the trick.