How to declare an object using markup in ASP.NET

Question

Assume we have a Person class:

public class Person
{
  public string FamilyName {get;set;}
  public string GivenName {get;set;}
}

And there's a control to somehow display the information of a list of persons. Here is the pseudocode of the aspx:

<uc1:EmployeesViewer runat="server">
  <Employees>
    <Person>
      <GivenName>John</GivenName>
      <FamilyName>Kerry</GivenName>
    </Person>
    <Person>
      <GivenName>Jack</GivenName>  
      <FamilyName>Lew</GivenName>
    </Person>
  <Employees>
</uc1:EmployeesViewer>

EmployeesViewer.Employees is of type List<Person>, with the attribute [PersistenceMode(PersistenceMode.InnerProperty)].

But Visual Studio doesn't compile this. Is it possible to declare a Person object using markup?

Answer 1

Is it possible to declare a Person object using markup?

Yes, with only some minor changes to the markup (and no changes to your Person class):

<%@ Page Language="C#" CodeBehind="DemoPage.aspx.cs" Inherits="DemoApp.DemoPage" %>
<%@ Register TagPrefix="uc1" Assembly="DemoApp" Namespace="DemoApp" %>

<uc1:EmployeesViewer runat="server">
    <Employees>
        <uc1:Person GivenName="John" FamilyName="Kerry" />
        <uc1:Person GivenName="Jack" FamilyName="Lew" />
    </Employees>
</uc1:EmployeesViewer>

The uc1: tag prefix assumes that your Person class is in the same assembly and namespace as EmployeesViewer. If not, just <%@ Register %> another tag prefix for Person.

Note: You can use the <uc1:Person> syntax even though Person doesn't derive from Control:

namespace DemoApp
{
    public class Person
    {
        public string FamilyName {get;set;}
        public string GivenName {get;set;}
    }
}

Here's a simple EmployeesViewer control that renders the list of employees:

namespace DemoApp
{
    [ParseChildren(true)]
    [PersistChildren(false)]
    public class EmployeesViewer : Control
    {
        private readonly List<Person> _employees = new List<Person>();

        [PersistenceMode(PersistenceMode.InnerProperty)]
        public List<Person> Employees
        {
            get { return _employees; }
        }

        protected override void Render(HtmlTextWriter writer)
        {
            foreach (Person person in this.Employees)
            {
                writer.RenderBeginTag(HtmlTextWriterTag.P);
                writer.WriteEncodedText(string.Format("{0} {1}", person.GivenName, person.FamilyName));
                writer.RenderEndTag();
            }
        }
    }
}

The [ParseChildren(true)] attribute is needed so that at run time ASP.NET interprets the <Employees> tag as a property name rather than as literal markup to be rendered.

The [PersistChildren(false)] and [PersistenceMode(PersistenceMode.InnerProperty)] attributes are needed so that, if at design time you modify the Employees collection using the designer's Properties window, Visual Studio correctly persists the collection to markup.