ASP.NET Web PDF Document Viewer/Editor Control Library

You calibrate your success by the number of rows you ve affected. Because the query is filtering on the primary key of the table, it will always affect, at most, only one row. So it either affects zero or one rows. If it affects one, your query has succeeded, which will only ever occur if a change has not been made to the row since it was read. If a change has been made (or the row has been deleted), the edit has been done with a dirty read, and you inform the user that there s been a concurrency error. This is a simplified example; in an actual application, you would use this branch of code to render whatever interface is required to deal with the concurrency error, enabling the user to resolve it. Concurrency is a problem that must be solved in any distributed application. How the problem gets solved is going to depend on your business rules and how much control you have over the schema of the database you re interacting with. Hopefully some of the techniques we ve gone over in this section will give you some ideas for meeting the requirements of your specific application.

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// Delegate the remaining members to the underlying worker member x.RunWorkerAsync() = worker.RunWorkerAsync() member x.CancelAsync() = worker.CancelAsync()

In the final chapter, you ll learn why it is critical for a JDBC programmer working with Oracle databases to learn and master PL/SQL. You ll also examine a few selected PL/SQL techniques that will help you in writing high-performance and maintainable PL/SQL code.

The Appendix includes two reference tables that list mappings between SQL object types and Java types.

The types inferred for the code in Listing 13-2 are as follows: type IterativeBackgroundWorker<'state> = new : ('state -> 'state) * 'state * int -> IterativeBackgroundWorker<'state> member RunWorkerAsync : unit -> unit member CancelAsync : unit -> unit member member member member ProgressChanged WorkerCompleted WorkerCancelled WorkerError : : : : IEvent<int * 'state> IEvent<'state> IEvent<unit> IEvent<exn>

Summary

The book is best read in sequential order. If you do want some flexibility in the order in which you read the book, then please follow these guidelines. To begin with, I recommend you read s 1 through 7 in sequential order. The remainder of the book is divided into two (more or less) self-contained parts. The first part consists of s 8 through 11, which describe Oracle objects and how to use them in JDBC. You should read these chapters in sequential order. The second part consists of s 12 through 17, which are fairly self-contained and can be read in any order, except for the fact that you may want to read 13 before 14.

Let s take a look at this signature first, because it represents the design of the type. The worker constructor is given a function of type 'state -> 'state to compute successive iterations of the computation, plus an initial state and the number of iterations to compute. For example, you can compute the Fibonacci numbers using the following iteration function: let fibOneStep (fibPrevPrev:bigint,fibPrev) = (fibPrev, fibPrevPrev+fibPrev);; The type of this function is as follows:

I welcome any comments or questions you may have about the book. You may contact me at rmenon.us@gmail.com.

There s a new data access model in the .NET Framework. This model is very different from ADO and OLEDB, because it dedicates types to specific databases. Vendors create a Managed Provider by implementing a known set of interfaces defined in the System.Data assembly. There are two main data access models in .NET. One is a low memory footprint, read-only data access model, and the other is an in-memory result set model. Both are tailored for different tasks, and as a .NET database developer, you should be aware of which model to use in which circumstances. Version 2.0 of the Framework adds many improvements to Managed Providers of data access, including a Provider Factory model, a configuration file entry dedicated to connection strings, and a very easy facility for encrypting these strings. The DataTable object also has a lot of new functionality; new features enable it to do all of the operations for a single result set that used to require a DataSet and DataAdapter. Finally, in a disconnected architecture, the problems of latency and concurrency must be handled. We examined a number of strategies for doing this in different circumstances. There are many more features for data access in the .NET Framework in version 2.0. In 11, we ll examine some of these, including SQL cache dependencies and data source controls.