This topic Handling Null Database Values Using Data Source Controls has now been updated on MSDN to fix the sample based on various customer feedback. You can still see the old version here, in case you're curious to compare both versions.

What has changed:

• In the previous sample, the two-way data-binding was not in place, so editing was not working. If you noticed that and tried to replace the Eval() statement by a Bind() statement in the EditItemTemplate, it wouldn't work either. Bind() statements don't support being encapsulated by other method calls as Eval() statements do. (A good explanation for that can be found in Eilon's blog).
• The previous sample was already using a great technique for handling null values, the AppendDataBoundItems property was set to true in the DropDownList control. The AppendDataBoundItems property enables you to populate the DropDownList control with both static items and data generated from the data source. However, the value for the null entry was set to zero. So every time a null value was read from the database, it had to be converted to zero. Changing the item list to an empty value did the trick here. The empty value is now automatically converted to null without the need to use a function for that (because the ConvertEmptyStringtoNull property of both the TemplateField and the data source control parameter is set to true).

Take a look and let us know if you think this has improved or if you still think it needs some work!

Soma, senior VP of the Developer Division, just announced on his blog that the Service Pack 1 for VS 2008 and .NET FX 3.5 are released!

That means that Dynamic Data is released and the documentation for Dynamic Data (and for the entire SP1) is now published on MSDN!

This is how the Table of Contents for Dynamic Data looks like for this release:

• Using Dynamic Data
• ASP.NET Dynamic Data Overview
• ASP.NET Dynamic Data Infrastructure
• ASP.NET Dynamic Data Guidelines
• Walkthrough: Creating a New Dynamic Data Web Site Using Scaffolding
• Walkthrough: Adding Dynamic Data to an Existing Web Site
• + ASP.NET Dynamic Data Scaffolding and Page Templates Overview
• + Adding Dynamic Behavior to ASP.NET Data-bound Controls
• + ASP.NET Dynamic Data Field Templates Overview
• + ASP.NET Dynamic Data Model Overview

We introduced some new cool features with this release for the ASP.NET documents.

1. Video tutorials
• Creating a New ASP.NET Dynamic Data Web Site Using Scaffolding
• Customizing Default Field Templates in ASP.NET Dynamic Data Applications
• Customizing the Appearance and Behavior of Data Fields in the Data Model for ASP.NET Dynamic Data
2. Runnable samples

The runnable samples are nothing new for the ASP.NET team, but this is the first time we are publishing them outside the ASP.NET site. Some topics that include runnable samples are the following:

• DynamicControl class
• DynamicField class
• UIHint property
• DynamicQueryStringParameter class
• How to: Customize Data Field Validation in the Data Model
• How to: Use ASP.NET Dynamic Data in Templated Data-Bound Controls
• How to: Customize Data Field Appearance and Behavior in the Data Model
• How to: Customize Data Field Validation in the Data Model Using Custom Attributes

Well, now you can tell us what you think of the documentation and the new features. The easiest way to do it is just to send your feedback through the rating system on the MSDN site (the stars on the right-upper corner of the topic).

Enjoy it!

You've created a custom attribute to use in your Dynamic Data application that has the AllowMultiple property set to true. When you read the MetaColumn.Attributes property (if the attribute is applied to a data field) or you read the MetaTable.Attributes property (if the attribute is applied to a table), you don't see the multiple attributes of the same type in the list, only the first one is returned.

Why?

The TypeDescriptionProvider class internally constructs a collection of attributes and filters out identical attributes. It determines whether an attribute is identical or not by examining the TypeId property. By default, the TypeId property returns the type of the attribute. Since both attributes are of the same type, only the first one is retrieved and the remaining ones are considered identical.

To fix this problem, you need a way to distinguish each attribute instance. The easiest way to do that is to override the TypeId property in your custom attribute implementation and simply return the current instance, like the following:

public override object TypeId
{
  get
  {
    return this;
  }
}