SmartDate in C#

Encoder PDF-417 2d barcode in C# SmartDate

The SmartDate type is a struct that contains and extends a DateTime value. It is discussed in 2 from a design perspective. The type is declared like this: [Serializable] [System.ComponentModel.TypeConverter( typeof(Csla.Core.TypeConverters.SmartDateConverter))] public struct SmartDate : Csla.Core.ISmartField, IComparable, IConvertible, IFormattable, Csla.Serialization.Mobile.IMobileObject

The IMobileObject interface exists to support serialization through the MobileFormatter, which is part of CSLA .NET for Silverlight. CSLA .NET for Silverlight is outside the scope of this book, and IMobileObject has no impact on how CSLA .NET works within the .NET runtime.

Not only is this type Serializable but it has a custom type converter, specified by the TypeConverter attribute. In fact, SmartDate is a very complex type because it implements operators, type converters, and various other .NET features to act as closely as possible to the DateTime type.

The ISmartField interface, defined in Csla.Core, is used to allow the rest of the CSLA .NET framework to interact with any smart data types such as this that add string parsing and the concept of being empty to a type. You can implement ISmartField to create your own smart types such as SmartInt or SmartDouble, but be aware that your type will also need to override many operators and provide type converters much like SmartDate in order to act as a first-class type in .NET.

The Utilities class contains utility methods that are used by other parts of the CSLA .NET framework. Many of these methods abstract the use of the .NET type system and reflection. Table 6-5 lists the methods in this class.

Provides functionality comparable to the VB runtime IsNumeric() function; determines whether a value can be converted to a number Provides functionality comparable to the VB runtime CallByName() function; calls a property or method by name, using reflection Gets the type returned by a property, returning the primitive type even if the value is Nullable<T> Gets the type of the items contained in a list or collection Coerces a value from one type into another type; somewhat like doing a cast but far more aggressive and powerful

While these methods exist primarily to support the CSLA .NET framework itself, they are public and can be used by business or UI code as well. In particular, IsNumeric(), CallByName(), and CoerceValue() can be useful in many scenarios. The Csla namespace includes other types beyond those discussed in this chapter. The classes discussed here, and all the rest of the classes, exist to support important features such as data binding, business and validation rules, authorization rules, the data portal, LINQ to CSLA, and so forth. As I discuss each subsystem in s 7 through 14, you ll get a full understanding of all the types.

The Csla.Core namespace contains types that are not intended for daily use by business developers. Rather, these types are intended for use by the CSLA .NET framework itself and to enable advanced scenarios such as extending or customizing CSLA .NET. This is a primary motivation for putting them into their own namespace to help keep them out of sight of business developers during normal development.

One primary use for the types in Csla.Core is to allow people to extend the framework. For instance, Core.BusinessBase could easily act as a starting point for creating some different or more advanced BusinessBase-style class. Likewise, Core.ReadOnlyBindingList is useful as a base for creating any type of read-only collection that supports data binding. There are also numerous interfaces in Csla.Core, which are very useful if you are building a UI framework that interacts with business objects. The base classes exposed by CSLA .NET are generic types, such as BusinessBase<T>. While generics are a powerful tool, they have a major drawback in that generic types are not polymorphic. For example, a List<string> and List<int> are two different types that do not inherit from List<T>. In fact, their common base type is IList, which is not a generic type. The same thing is true for BusinessBase<Customer> and BusinessBase<Product>. If you want to write code that can work with either type, you need to fall back to Csla.Core.BusinessBase, which is not a generic type. But if you want more focused behavior, such as the ability to save any editable object, you d want to use the Csla.Core.ISavable interface. That interface is implemented by both BusinessBase and BusinessListBase because both support editable objects that can be saved. Table 6-6 lists the most commonly used classes and interfaces in Csla.Core.