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The class defines two events, DataPortalInvoke and DataPortalInvokeComplete: public static event Action<DataPortalEventArgs> DataPortalInvoke; public static event Action<DataPortalEventArgs> DataPortalInvokeComplete; private static void OnDataPortalInvoke(DataPortalEventArgs e) { Action<DataPortalEventArgs> action = DataPortalInvoke; if (action != null) action(e); } private static void OnDataPortalInvokeComplete(DataPortalEventArgs e) { Action<DataPortalEventArgs> action = DataPortalInvokeComplete; if (action != null) action(e); } These follow the standard approach by providing helper methods to raise the events. Also notice the use of the Action<T> generic template. This is provided by the .NET framework as a helper when declaring events that have a custom EventArgs subclass as a single parameter. There s also a corresponding EventHandler<T> template to help when declaring the standard sender and EventArgs pattern for event methods.

Under certain conditions, you can assign an object to an array element even if the object is not of the array s base type. This property of arrays is called array covariance. You can use array covariance if the following are true: The array is a reference type array. There is an implicit or explicit conversion between the type of the object you are assigning and the array s base type.

The business assembly is the sole location for implemented business logic and the final destination for incoming service requests. The previous listing looks very spare because it does not show the implementation code for any of the methods. You can refer to the sample project to view the full code listing. Very little implementation code is shown in this chapter because it is of secondary importance. It is more important that you feel comfortable with the interfaces and the architecture of the components.

There is another option that s even simpler. The GetXYZCommandWrapper methods have another overloaded method signature that accepts a parameter array as a second parameter. This parameter array will accept all the values for the procedure s input parameters. The command wrapper factory then makes a request to the database for the schema definition of the procedure being executed. Using this information, it generates the set of parameters the procedure expects. Our last example could use this technique with the following code: private PublisherBO GetPublisherParamCache(string PubID) { PublisherBO boReturn = new PublisherBO(); Database db = DatabaseFactory.CreateDatabase(); DBCommandWrapper cw = db.GetStoredProcCommandWrapper("usp_GetPubDetails", PubID); db.ExecuteNonQuery(cw); boReturn.PubID = PubID; boReturn.Name = cw.GetParameterValue("@pub_name").ToString(); boReturn.City = cw.GetParameterValue("@city").ToString(); boReturn.State = cw.GetParameterValue("@state").ToString(); boReturn.Country = cw.GetParameterValue("@country").ToString(); return boReturn; } Here you ve replaced all of the calls to create parameters and simply added the PubID as a second argument passed to the factory method. Notice that even though you haven t explicitly

The iPod touch 4 s new App Switcher program means you can now easily jump between any two apps. There may be times when you want to jump between your Email and your Calendar apps to copy-and-paste information. The information to copy-andpaste could be anything, such as driving directions or critical notes you need at your fingertips for a meeting. Follow these steps to copy-and-paste information between your Email and Calendar programs: