Stumped With Custom Property on User Control - asp.net

Question

I have created an ASP.NET usercontrol. When I explicity provide the value for a custom property, the value is passed to the control. However, when I try to use the value from a datasource, the value is not passed to the control.
The user control sits within a FormView. The FormView successfully displays the underlying record. I am attempting to pass to the control a value in a column from the FormView's datasource. This works
<asp:formview .... />
<editTemplate>
<uctrl:DateSelector ID="DateSelector1" runat="server" DateValue="5/30/2011" /><br />
<%#Eval("MilestoneDate")%>
</editTemplate>
</asp:formview>
This does not...
<asp:formview .... />
<editTemplate>
<uctrl:DateSelector ID="DateSelector1" runat="server" DateValue='<%#Eval("MilestoneDate")%>' /><br />
<%#Eval("MilestoneDate")%>
</editTemplate>
</asp:formview>
I have confirmed that MileStoneDate does have a value in it. For whatever the reason, the value is not being passed to the control, however the control does recognize a literal value.
Imports Microsoft.VisualBasic
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.UI
Imports System.ComponentModel
Partial Class content_WebUserControl
Inherits System.Web.UI.UserControl
<Bindable(True, BindingDirection.OneWay)>
Public Property DateValue() As String
Get
Return _DateValue
End Get
Set(ByVal value As String)
_DateValue = value
End Set
End Property
Private _DateValue As String
Protected Sub Page_Load() Handles Me.Load
If IsDate(Me.DateValue) Then
Dim NewDate As DateTime = CDate(Me.DateValue)
LabelSelectedDateDisplay.Text = Me.DateValue
LabelSelectedDateDisplay_DayOfWeek.Text = NewDate.ToString("dddd")
TextBoxSelectedDate.Text = Me.DateValue
Else
LabelSelectedDateDisplay.Text = ""
LabelSelectedDateDisplay_DayOfWeek.Text = ""
TextBoxSelectedDate.Text = ""
End If
End Sub
End Class
I was refered to the post at this URL ASP.NET User Control : can't initialize a user control property using Eval("...")
However, based on my understanding of the post, what I have should be working.

Answer 1

You need to use ViewState to persists DateValue between page requests.
Public Property DateValue() As String
Get
IF IsNothing(ViewState("datevalue") Then
return String.Empty
End If
return ViewState("datevalue").ToString()
End Get
Set(ByVal value As String)
ViewState("datevalue")=value
End Set
End Property
Or store value directly to the controls:
Public Property DateValue() As String
Get
Return LabelSelectedDateDisplay.Text
End Get
Set(ByVal value As String)
If IsDate(value) Then
Dim NewDate As DateTime = CDate(value)
LabelSelectedDateDisplay.Text = NewDate
LabelSelectedDateDisplay_DayOfWeek.Text = NewDate.ToString("dddd")
TextBoxSelectedDate.Text = NewDate
Else
LabelSelectedDateDisplay.Text = ""
LabelSelectedDateDisplay_DayOfWeek.Text = ""
TextBoxSelectedDate.Text = ""
End If
End Set
End Property

Answer 2

The problem is that databinding doesn't occur on your formview until after Page.Load, and you are checking the value of the property during that time. If you want the value to be set in Page.Load you need to manually bind using FormView.Databind().
Alternatively, you can change the code you listed in your custom control from handling Page.Load to handle Page.Prerender, if nothing requires that code to execute earlier.

Answer 3

It looks like the issue might be timing/event related.
When you set a property with <%# %>, the value is assigned to the property during the Control's databinding event. If you look for it at Page_Load() time, it won't be there yet.
If you change your code to check the value in the PreRender event, it should be there.