James Gregory

I’ve updated the ObjectField to be considerably simpler than it was before. While writing my Data-binding hierarchical objects post I wrote this about the BoundField implementation:

Using a TypeDescriptor to get the property… This strikes me as a bit odd to be honest, because the DataBinder has the ability to evaluate a hierarchical path.

Which is interesting, because I was using a TypeDescriptor in my ObjectField implementation!

Originally, the ObjectField was using the method below to evaluate the hierarchical paths, which to be honest is a bit verbose.

private object GetNestedValue(object component, string field)
{
	string[] properties = field.Split('.');

	foreach (string property in properties)
	{
		PropertyDescriptor descriptor =
			TypeDescriptor.GetProperties(component).Find(property, true);

		if (descriptor == null && !AllowNulls)
		{
			// no descriptor, and we're not allowing nulls so complain that
			// we can't find the object
			throw new HttpException(string.Format(MissingFieldErrorMessage,
				property));
		}
		else if (descriptor == null)
		{
			// silently return, with the NullValue if present
			component = NullValue;
			break;
		}

		component = descriptor.GetValue(component);
	}

	return component;
}

The GetNestedValue method was splitting the DataField value and then recursively evaluating each property.

Here’s the same implementation using the DataBinder:

// looking to bind against child-objects
object component = DataBinder.GetDataItem(controlContainer);

return DataBinder.Eval(component, DataField);

Magic!

As a side effect of this change, the ObjectField can now support everything regular data-binding does. So you can use indexers and such in your DataField now.

A couple of other things you should know: the AllowNulls property has been removed because it’s no longer supported, and the NullValue field has also been removed because the BoundField already supported it in the form of NullDisplayText.

Downloads

The ObjectField is open-source under the new BSD License; read the license for what you’re allowed to do.

You can download the source here: Download Source.
You can download the latest binary here: Download Binary.

The source is also accessible from Subversion at: http://jagregory.googlecode.com/svn/trunk/ObjectField/ (using user jagregory-read-only)