dotConnect Team’s Blog

Article was updated on 3/4/2010

This article can be useful for programmers who want to develop a cross-database applications and use the canonical functions.

Entity Framework Canonical Functions are a set of functions, which are supported by all Entity Framework providers. These canonical functions will be translated to the corresponding data source functionality for the provider.

The tables below contain information about these functions supported by the Devart products.
Functions supported by the following DBMS: MySQL, PostgreSQL, Oracle, SQLite, SQL Server 2005, and SQL
Server 2008 are marked with green.

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Introduction

In this article we consider how to build Entity Framework models using PostGIS objects in Entity Developer. PostGIS is a popular spatial extension for PostgreSQL that gives one an opportunity to work with geographic objects. To create and use such models we will:

• use a .NET wrapper for PostGIS (SharpMap)
• build a new Entity C# code generation template in order to enable geometry types support
• write some code dealing with change tracking

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Go to devart.uservoice.com and share your ideas about new features you want to see in Entity Developer. There you may vote for features that are already in our roadmap, and they will have higher priority in our plans, or you may suggest your own features, and if they will get enough votes, we will include them to the roadmap. Your opinion helps us to make Entity Developer better and more useful for you.

Currently Entity Developer roadmap includes the following features:
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Entity Framework

In this article we consider a short description of the Entity Framework and LINQ to SQL transactional models. There are also some simple code listings illustrating different aspects of the transactional model.

A transaction is a series of operations performed as a single unit of work. Entity Framework transactions are a part of its internal architecture. The SaveChanges method operates within a transaction and saves results of the work. It is designed to ensure data integrity. The common reason of integrity problems is a Concurrency violation, which can be raised during the saving process. Concurrency violation occurs an OptimisticConcurrencyException in this case. To resolve this conflict you have to call the Refresh method with the StoreWins or ClientWins value, and after that call SaveChanges again. But be aware, that the Refresh with the ClientWins option can be a source of problem too. It rewrites all changes made to the data after context query execution.
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New version of Entity Developer comes with completely redesigned template system, which allows much more comfortable template editing and much more flexible code generation.

Code Generation

New template framework allows you to create additional templates for a wide range of tasks:

• Generating code for other languages than Visual Basic and C#
• Use custom base class
• Generate classes without namespace (for example, in Visual Basic, where project has implicit namespace)
• Implement GetHashCode() and Equals() for the class, which allow to add entities into HashTable.
• Implement default value setting for properties
• Create an interface, which contains only public properties, for a class
• IPOCO
• Property validation

New T4 like template language features the full power of C# or Visual Basic in the templates, allowing virtually anything you may want for code generation. Organizing iterated or conditional output has never been easier. You may even import your own assemblies and use classes from them.
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When designing model, and especially when debugging it, it is often necessary to view and edit table and view data or fill tables with some test data. Now Entity Developer allows viewing and editing data of tables, views, and model entities, create and execute LINQ to SQL and Entity SQL queries against the model, eliminating the need for additional applications and reducing time for accessing these operations.

Editing Database Data

Entity Developer allows you to directly edit database data in the tables or views. Just right-click the table or view in the Database Explorer window and choose Retrieve Data from the popup menu. A new window will open with two tabs: Data and SQL.

SQL tab contains the SQL query to the specified table or view. Data tab displays table or view data, which you can edit.

To edit data in the cell click on a cell you want to edit. After making any changes to the cell, press to confirm changes or ESCAPE to cancel. To add a new record, click the ‘+’ button under the grid. To delete a record from the grid, click the ‘-’ button under the grid. You may also use grid popup menu for insert and delete operations.
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According to the list of core functions in SQLite, there is no native support for the most mathematics functions (sqrt, log, etc). Furthermore, user may need non-standard functions for his own task (e.g. conversion Celsius to Fahrenheit). This issue can be resolved with user-defined functions (UDFs).

Support for UDFs is added to dotConnect for SQLite starting with the 2.50 version. UDF provides a mechanism for extending the functionality of the SQLite engine by adding a function that can be evaluated in the SQL statements of SQLiteCommand. For more information, please refer to our documentation to the SQLiteAggregateFunction, SQLiteCollationFunction, SQLiteScalarFunction classes (there are samples of using them). Full support for user-defined functions and collating sequences means that in many cases if SQLite doesn’t have a feature, you can write it yourself in your favorite .NET language. Writing UDF’s and collating sequences has never been easier.
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According to this post in the ADO .NET team blog, Microsoft deprecates OracleClient as a part of ADO.NET roadmap. Microsoft strongly recommends customers to use  third-party ADO.NET providers for Oracle  instead of continuing to use Microsoft’s OracleClient for new application development.

Devart offers dotConnect for Oracle – fast and reliable ADO.NET provider for the wide range of users. Our ADO.NET provider is the most compatible with OracleClient provider, and it provides the easiest migration from OracleClient. It allows you to migrate easily without effort.
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Users often ask us how to use Oracle stored routines, returning REF CURSORs, in Entity Framework models with dotConnect for Oracle. So, we decided to post here a walkthrough, that describes how to create Entity Framework model with stored procedures in Entity Developer and EDM Designer. It tells how to create methods, based on Oracle stored procedures and functions, returning REF CURSOR parameters, and how to use the stored procedures for mapping insert, delete, and update operations.

In order to complete this walkthrough, you will need access to the Oracle database server 9.2.0.4 or higher. You also need dotConnect for Oracle Professional Edition 5.25 or higher. Microsoft Visual Studio 2008 SP1 or Visual Studio 2010 is also required.
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