C# 4 and .NET 4

1272 ❘ ChaPTer 42 Asp.net dynAmic dAtA And mvc
Next, note that a property called ModelState.IsValid is used to check that the model passed to the
method is valid, and if not the method simply returns the create view with no parameters. If this happens,
the validation summary and validation errors will be displayed, as shown in Figure 42-15.
figure 42-15
If there are no errors, the new item is added through the ADO.NET Entity Framework-defined
AddToProducts() method, and the page redirects to the list view as follows:
entities.AddToProducts(productToCreate);
entities.SaveChanges();
return RedirectToAction("Index");
An important point to note here is that the validation can be controlled through data annotations,
introduced earlier in the chapter. Most of the default validation comes automatically from the constraints on
data in the database, but you may want to modify this behavior. For example, you could limit the number of
characters for a product name with the following two classes:
using System.ComponentModel.DataAnnotations;
namespace PCSMVCMagicShop.Models
{
[MetadataType(typeof(ProductMetadata))]
public partial class Product
{
}
}
code snippet PCSMVCMagicShop/Models/Product.cs
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