Nested Repeaters in ASP.NET

I've found that the simplest way to do nested repeaters without worrying about databinding events is to just set the DataSource using <%# %> syntax.

For example:

<asp:Repeater runat="server" id="Departments">  <ItemTemplate>    Name: <%# Eval("DeptName") %>    Employees:    <asp:Repeater runat="server" DataSource='<%# Eval("Employees") %>'>      <ItemTemplate><%# Eval("Name") %></ItemTemplate>      <SeparatorTemplate>,</SeparatorTemplate>    </asp:Repeater>  </ItemTemplate></asp:Repeater>

This is presuming that your Departments class has an Employees property - eg:

public class Department {  public string DeptName {get; set;}  public IEnumerable<Employee> Employees {get; set;}}public class Employee {  public string Name {get; set;}}

If your outer-repeater object doesn't have a property corresponding to the inner-repeater object you can still use this trick, by adding a method in your code-behind that does the calculation. So your inner repeater might become:

<asp:Repeater runat="server" DataSource='<%# GetEmployees(Container.DataItem) %>'>

and then GetEmployees might look something like:

protected IEnumerable<Employee> GetEmployees(object item) {  var dept = (Department) item;  // then do whatever is necessary to get the employees from dept  return employees;}

It's always cleaner to deal with the datasource than messing about with ItemDataBound, but this is even more the case when nesting Repeaters:

<asp:Repeater DataSource="<%#ColOfCol%>" runat="server">  <ItemTemplate>    <tr>      <asp:Repeater DataSource="<%#Container.DataItem%>" runat="server">        <ItemTemplate>          <td><%#SomeExtractingMethodLikeEval()%></td>        </ItemTemplate>      </asp:Repeater>    </tr>  </ItemTemplate></asp:Repeater>

The inner datasource could also be an evaluated property, or a call to a method that returns the enumeration wanted. Just be aware that it will be called with an object. I prefer to write the specific version, and then overload:

protected IEnumerable<string> GetNames(Family fam){  foreach(Person p in fam.Members)    yield return p.FirstName + " " + p.Surname;}protected IEnumerable<string> GetNames(object famObj){    return GetNames((Family)famObj);}

One thing to be aware of is that if you want to get the current object in the parent repeater than you have to obtain it with:

((RepeaterItem)Container.Parent.Parent).DataItem

You can nest repeaters without a problem. More then 2 levels deep gets nasty though. Here's how:

The html looks something like this:

<asp:Repeater ID="r1" runat="server" OnItemDataBound="r1_ItemDataBound"><ItemTemplate><!-- top level repeater element template here -->    <asp:Repeater ID="r2" runat="server" onitemdatabound="r2_ItemDataBound">    <ItemTemplate><!-- child repeater element template here -->    </ItemTemplate>    </asp:Repeater></ItemTemplate></asp:Repeater>

The codebehind looks like this:

    protected void r1_ItemDataBound(object sender, RepeaterItemEventArgs e) {        Repeater r2 = (Repeater)e.Item.FindControl("r2");        r2.DataSource = yourDataSourceHere; // you'll have to query for appropriate data        r2.DataBind();    }    protected void r2_ItemDataBound(object sender, RepeaterItemEventArgs e) {        // do the same thing here for the 3rd nested repeater if you have a third, and so on    }