Posted on Friday November 2012
UPDATE: Well I've fleshed this out a little. Source is available, with model binding and DataAnnotation validations.
I was a bit unhappy with my previous attempt at model binding, so I've had a bit more of a read and play.
Firstly, it's great to see the RepeaterItem has an ItemType property. Up until now I would do something like:
<asp:Repeater runat="server">
<ItemTemplate>
<label>Product</label>
<input type="text" value="AsProductViewModel(Container).Name" />
</ItemTemplate>
</asp:Repeater>
protected ProductViewModel AsProductViewModel(RepeaterItem item)
{
return item.DataItem as ProductViewModel;
}
By setting ItemType I can now access the properties directly.
<asp:Repeater runat="server" ItemType="WebApplication2.ProductViewModel">
<ItemTemplate>
<label>Product</label>
<input type="text" value="<%# Item.Name %>" />
</ItemTemplate>
</asp:Repeater>
And that makes me pretty happy.
UPDATE: No, that is just all wrong. This applies to .NET 4.5. Prior to that there is no ItemType property available, so back to using the AsModel helper. Bugger.
But better (maybe if you think using the built in WebControls is better...) was reading this fairly old post off MSDN on binding WebControls back to an object. This was rather similar to what I had made earlier. The article has the good idea of looking for .Text or .Value property names, rather than testing for a specific control. I have gone for a possibly less flexible approach and test for the least derived class I can think of, e.g. ListControl will capture DropDownList, CheckBoxList etc.
On reflection (ha!) I think the original authors idea might be better. It's fairly conventional to have a .Text property if you have some sort of text editing control, but there is no guarantee you derived from TextBox... ah well, back to the drawing board.
<asp:Repeater ID="TestRepeater" runat="server" ItemType="WebApplication2.Product">
<ItemTemplate>
<asp:TextBox runat="server" ID="name" Text="<%# Item.name %>" />
<asp:TextBox ID="id" runat="server" Text="<%# Item.id %>" />
<asp:CheckBox runat="Server" ID="isSelected" Checked="<%# Item.isSelected %>" />
<asp:DropDownList runat="server" ID="age" name="product[0].age" SelectedValue='<%# Item.age %>'>
<asp:ListItem Value="21" />
<asp:ListItem Value="31" />
<asp:ListItem Value="41" />
</asp:DropDownList>
<asp:Calendar runat="server" ID="MyDate" SelectedDate="<%# Item.MyDate %>" />
</ItemTemplate>
</asp:Repeater>
using System;
using System.Collections.Generic;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebApplication2
{
public partial class _Default : Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
Bind();
}
protected void SomeButton_Click(object sender, EventArgs e)
{
var pp = RepeaterToModel<Product>(TestRepeater);
}
private void Bind()
{
var products = new List<Product>();
products.Add(new Product() { name = "test1", id = 1, age = 31 });
products.Add(new Product() { name = "test2", id = 2, age = 31 });
products.Add(new Product() { name = "test3", id = 3, age = 21 });
TestRepeater.DataSource = products;
TestRepeater.DataBind();
}
private IEnumerable<T> RepeaterToModel<T>(Repeater repeater) where T : new()
{
var results = new List<T>();
foreach (RepeaterItem item in repeater.Items)
{
var result = ControlToModel<T>(item);
results.Add(result);
}
return results;
}
private T ControlToModel<T>(Control source) where T : new()
{
var result = new T();
var properties = typeof(T).GetProperties();
foreach (var property in properties)
{
foreach (Control control in source.Controls)
{
if (control.ID == property.Name)
{
if (control is TextBox)
{
property.SetValue(result, AutoMapper.Mapper.Map((control as TextBox).Text, typeof(string), property.PropertyType), null);
break;
}
if (control is HiddenField)
{
property.SetValue(result, AutoMapper.Mapper.Map((control as HiddenField).Value, typeof(string), property.PropertyType), null);
break;
}
if (control is ListControl)
{
property.SetValue(result, AutoMapper.Mapper.Map((control as ListControl).SelectedValue, typeof(string), property.PropertyType), null);
break;
}
if (control is CheckBox)
{
property.SetValue(result, AutoMapper.Mapper.Map((control as CheckBox).Checked, typeof(bool), property.PropertyType), null);
break;
}
if (control is Calendar)
{
property.SetValue(result, AutoMapper.Mapper.Map((control as Calendar).SelectedDate, typeof(DateTime), property.PropertyType), null);
break;
}
break;
}
}
}
return result;
}
}
}
After a little more wine and a little benchmarking I now have this:
using System;
using System.Collections.Generic;
using System.Reflection;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebApplication2
{
public class WebFormModelBinder
{
private readonly Dictionary<string, PropertyInfo> _controlPropertyCache = new Dictionary<string, PropertyInfo>();
public IEnumerable<T> RepeaterToObjects<T>(Repeater repeater) where T : new()
{
var results = new List<T>();
foreach (RepeaterItem item in repeater.Items)
{
results.Add(ControlToObject<T>(item));
}
return results;
}
public T ControlToObject<T>(Control source) where T : new()
{
var result = new T();
var properties = typeof(T).GetProperties();
foreach (var property in properties)
{
foreach (Control control in source.Controls)
{
if (control.ID == property.Name)
{
if (TryFindAndSetObjectProperty<T>(control, "Checked", typeof(bool), result, property))
{
break;
}
if (TryFindAndSetObjectProperty<T>(control, "Text", typeof(string), result, property))
{
break;
}
if (TryFindAndSetObjectProperty<T>(control, "Value", typeof(string), result, property))
{
break;
}
if (TryFindAndSetObjectProperty<T>(control, "SelectedValue", typeof(string), result, property))
{
break;
}
if (TryFindAndSetObjectProperty<T>(control, "SelectedDate", typeof(DateTime), result, property))
{
break;
}
break;
}
}
}
return result;
}
private bool TryFindAndSetObjectProperty<T>(Control source, string sourcePropertyName, Type sourcePropertyType, T destination, PropertyInfo destinationPropertyInfo)
{
if (_controlPropertyCache.ContainsKey(source.ID))
{
destinationPropertyInfo.SetValue(destination, Convert.ChangeType(_controlPropertyCache[source.ID].GetValue(source, null), destinationPropertyInfo.PropertyType), null);
return true;
}
var properties = source.GetType().GetProperties();
foreach (var pi in properties)
{
if (pi.Name == sourcePropertyName && pi.PropertyType == sourcePropertyType)
{
try
{
destinationPropertyInfo.SetValue(destination, Convert.ChangeType(pi.GetValue(source, null), destinationPropertyInfo.PropertyType), null);
_controlPropertyCache[source.ID] = pi;
return true;
}
catch
{
return false;
}
}
}
return false;
}
}
}