Properties of WebUserControl are null in DataBind override - asp.net

Question

I have WebUserControl with DataBind override:
public partial class WebUserControl1 : System.Web.UI.UserControl
{
public object DataSource { get; set; }
public string Text { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
}
public override void DataBind()
{
// *** there when called, properties are null, why? ***
repeater2.DataSource = DataSource;
repeater2.DataBind();
}
}
This control is in repeater with declarative bounded properties:
<asp:Repeater ID="repeater" runat="server">
<ItemTemplate>
<WebUserControl1 runat="server" DataSource='<%# DataBinder.Eval(Container.DataItem, "levels") %>' Text='<%# DataBinder.Eval(Container.DataItem, "Text") %>' />
</ItemTemplate>
</asp:Repeater>
Now when i call DataBind() on repeater:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
... data query
repeater.DataSource = items;
repeater.DataBind();
}
}
in overriden control's DataBind() method i don't have properly setted properties DataSource and Text, they are null, why?

Answer 1

If you have only one repeater control in WebUserControl1, it is easier to bind that child repeater control in Repeater.ItemDataBound Event of Parent repeater.
Here is the sample -
ASPX
<asp:Repeater ID="ParentRepeater" runat="server" OnItemDataBound="ParentRepeater_ItemDataBound">
<ItemTemplate>
<asp:Label runat="server" ID="StreetLabel" /><br/>
<asp:Repeater ID="ChildRepeater" runat="server">
<ItemTemplate>
<asp:Label runat="server" ID="FirstNameLabel" />
<asp:Label runat="server" ID="LastNameLabel" />
</ItemTemplate>
</asp:Repeater><hr/>
</ItemTemplate>
</asp:Repeater>
Code Behind
public class Address
{
public int Id { get; set; }
public string Street { get; set; }
public List<User> Users { get; set; }
}
public class User
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ParentRepeater.DataSource = new List<Address>
{
new Address
{
Id = 1,
Street = "1st Street",
Users = new List<User>()
{
new User {Id = 1, FirstName = "John", LastName = "Doe"},
new User {Id = 1, FirstName = "Marry", LastName = "Doe"}
}
},
new Address
{
Id = 2,
Street = "2nd Street",
Users = new List<User>()
{
new User {Id = 1, FirstName = "Eric", LastName = "Newton"},
new User {Id = 1, FirstName = "John", LastName = "Newton"}
}
}
};
ParentRepeater.DataBind();
}
}
protected void ParentRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
var address = e.Item.DataItem as Address;
var streetLabel = e.Item.FindControl("StreetLabel") as Label;
streetLabel.Text = address.Street;
var repeater = e.Item.FindControl("ChildRepeater") as Repeater;
repeater.ItemDataBound += ChildRepeater_ItemDataBound;
repeater.DataSource = address.Users;
repeater.DataBind();
}
}
protected void ChildRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
var user = e.Item.DataItem as User;
var firstNameLabel = e.Item.FindControl("FirstNameLabel") as Label;
firstNameLabel.Text = user.FirstName;
var lastNameLabel = e.Item.FindControl("LastNameLabel") as Label;
lastNameLabel.Text = user.LastName;
}
}
Solution for Original Question
Delete public override void DataBind() event and bind repeaters2 inside PreRender event.
public partial class WebUserControl1 : System.Web.UI.UserControl
{
protected override void OnPreRender(EventArgs e)
{
repeater2.DataSource = DataSource;
repeater2.DataBind();
base.OnPreRender(e);
}
}