Nested Repeaters in ASP.NET

42
votes

I have a class that contains hierarchical data. I want to present this data in my ASP.net webapp using nested repeaters. How do I do this? I've only ever done one level of nesting, how do I do say five levels?

Each item can have zero or many sub items. I'm basically just indenting at each subleveling using some css stuff. I do not want to use the treeview control, I want to strictly stick with a repeater.

Update:
My data comes from a database. I have an item datatable with some basic properties.

Item
{
   ID,
   Name,
   Description,
   ...
}

Then I have a many to many table with:

Parent
{
   ParentID,
   ChildID
}

I'm iterating through each item and displaying its children; and its children's children. I assume this would best be accomplished with nested repeaters, but I could be wrong.

4
c#asp.netrepeaternested-repeater
What type of data are you showing? tabular data? lists? where is the data coming from? (you may end up with issues of many selects if you're getting from the database since you'll get a databind for each repeater) - Jaime
Send sample data your repeaters will show. - Amr Elgarhy
Don't understand the edit that was made. While I can't think of anything specific in 4.0 that would affect this, (A) I could be wrong, (B) how's the querant meant to know, if they did they wouldn't be asking this question. - Jon Hanna
The data is basically text, and it comes from a database. I just include what version of things I'm using so that solutions can be presented that target my enviroment. - Mike
@Jon: it's best to ask about what you don't understand, lest you remain ignorant. The information I removed from the title i already in the tags. It's redundant in the title. Also, C# is totally irrelevant to this question. The answer would be identical if Mike were using VB.NET, with the exception of a little syntax. Finally, "Hi", "Thanks", signatures and taglines are noise and don't belong in a Q&A site. Maybe in a discussion forum, which this is not. - John Saunders

4 Answers

36
votes

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
83
votes

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;
}
13
votes

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
    }
2
votes
<asp:Repeater ID="R1" runat="server">
    <ItemTemplate>
        <asp:Repeater ID="R2" runat="server">
        </asp:Repeater>
    </ItemTemplate>
</asp:Repeater>


R1.ItemDataBound += (s, e) =>
{
    var r2 = e.Item.FindControl("R2") as Repeater;
    r2.DataSource = something;
    r2.DataBind();
};

Be aware that FindControl is not recursive, it will only get the children.