Nested Repeaters in ASP.NET
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开发者_C百科 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.
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
}
<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.
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