Implementing Entity Validation - ASP.NET Dynamic Data - page 253

public interface IDynamicValidatorException
{
IDictionary<string, Exception> InnerExceptions { get; }
}
The built-in EntityDataSource control takes advantage of this interface when reporting
errors that occur when it tries to assign field values received from the form controls to the
properties of entity objects. The Entity Framework implements its own, limited, validation
based on the rules embedded directly in the entity data model (EDMX), such as prevent-
ing assignment of a null value to an entity property that does not allow it. When these
errors are detected, the EntityDataSource control collects all errors for a given entity
object and throws the EntityDataSourceValidationException , which implements the
IDynamicValidatorException interface. In the presentation layer, the DynamicValidator
controls check all exceptions thrown by the data source control, and if a particular excep-
tion implements the IDynamicValidatorException interface, the validator controls use its
InnerExceptions dictionary to find exceptions that apply to the entity properties they
validate.
Unfortunately, the IDynamicValidatorException is defined in the System.Web.Extensions
assembly and where the EntityDataSourceValidationException is defined in the
System.Web.Entity . This is not a problem for web applications; however, for other types
of applications, using these types means taking a dependency on ASP.NET, which is only
included in the full version of the .NET framework and not in the client profile.
Modifying ObjectContext to Report Multiple Errors
To avoid adding a dependency on the presentation framework to the business layer of the
application, you can use another built-in exception type - AggregateException . The .NET
Framework version 4 introduced this class in the System namespace to support reporting
of multiple errors in the Parallel Task Library (TPL). AggregateException also defines a
property called InnerExceptions , although it stores a ReadOnlyCollection of Exception
objects instead of a Dictionary . Here is how declaration of this class looks in simplified
form:
public class AggregateException : Exception
{
public ReadOnlyCollection<Exception> InnerExceptions { get; }
}
Here is a new version of the Validate method of the UnleashedObjectContext class that
reports multiple validation errors in a single AggregateException :
private void Validate(ObjectStateEntry stateEntry)
{
object entity = stateEntry.Entity;
var context = new ValidationContext(entity, null, null);
var results = new List<ValidationResult>();