Databases Reference
In-Depth Information
CHAPTER
8
IN THIS CHAPTER
.
Validation Framework
Validation
.
Customizing Entity Framework
Code Generation
.
Automated Testing
.
Declarative Validation
.
Imperative Validation
V
alidation of entities is one of the key aspects of
business logic. The .NET Framework introduced a new
validation framework in Service Pack 1 of version 3.5,
at the same time the first version of Dynamic Data was
released. This framework is implemented in the
System.ComponentModel.DataAnnotations
namespace and
contains a set of attributes and classes for validating objects
and their properties.
.
Validating Multiple Rules
.
Validating Entity State Changes
The Data Annotations namespace is defined in a separate
assembly called
System.ComponentModel.DataAnnotations
,
installed in the global assembly cache. This assembly is
referenced by default when you create a new Dynamic Data
project in Visual Studio. If, however, your entity classes are
located in a separate project, make sure it references this
assembly as well.
At the core of the validation framework is an abstract base
class called
ValidationAttribute
. It defines a virtual
method called
IsValid
, which takes an object to validate
and returns
true
if it is valid and false if it is not. Concrete
descendants of this class, such as the
RequiredAttribute
,
override the
IsValid
method to perform the actual
validation.
The validation attributes are applied to the things they vali-
date, such as properties, fields, or entire classes. Consider
the following example that defines a simple Product entity
class with a
required
property called
ProductName
:
