Visual Basic® 2010 Unleashed

Validating Data

As in LINQ to SQL, you can take advantage of partial methods to accomplish custom data validations; however, there is an important difference. Entity Data Model generation takes care of providing a better mapping between SQL Server types and .NET types. Chapter 25 provides an example of the custom validation rule for ensuring that a string is not greater than 20 characters. In the Entity Framework this is not necessary. For example, take a look at the Properties window showing properties for the Product.QuantityPerUnit property as previously shown in Figure 27.12.

Notice how there is a Max Length property that limits the size of the string to 20 characters. To understand what happens, try to run the AddProduct method previously ...