SQL Server 2008 Connection String Samples. Adding, Modifying, and Deleting Objects (Entity Framework) For example, suppose you execute a query that returns a SalesOrderHeader object and a collection of related SalesOrderDetail objects. You could enumerate through the collection and perform the following operations: The following example shows various changes to objects in an object context: SalesOrderHeader order = context.SalesOrderHeader.Where ("it.SalesOrderID = @id", new ObjectParameter( "id", orderId)).First(); // Change the status and ship date of an existing order. order.Status = 1; order.ShipDate = DateTime.Today; // Load items for the order, if not already loaded.if (!
When you want to insert data in the data source, you must create an instance of an entity type and add the object to an object context. Before you can add a new object, you must first set all properties that do not support null values. The following example uses the static CreateSalesOrderHeader method to create a new instance of the SalesOrderHeader class. The following considerations apply when adding new objects: 101 LINQ Samples. Mixing LINQ Providers and LINQ to Objects. Var records = this.CreateQuery<EntityType>() .Where(item => item.PartitionKey == region) .AsEnumerable() .OrderByDescending(item => item.DateUpdated); Notice the AsEnumerable() call in the middle of the query above.
Why do you suppose that was added to this query? Equally important, why do you suppose it was added at that location in the query? The answer lies in the design of Azure table storage, the TableServiceContext implementation of IQueryable<T>. There is a major difference between IEnumerable<T> and IQueryable<T>. An implementation built on IQueryable<T> produces expression trees that translate the query’s intent into a native language for a specific data source. That’s the key to this discussion: An implementation of IQueryable<T> translates an expression tree to a native representation of the same logic for its particular source type.
This is common behavior with most IQueryable implementation. That answers both questions I posed when I showed this sample. ADO.NET. ADO.NET is a set of classes that expose data access services for .NET Framework programmers. ADO.NET provides a rich set of components for creating distributed, data-sharing applications. It is an integral part of the .NET Framework, providing access to relational, XML, and application data. ADO.NET supports a variety of development needs, including the creation of front-end database clients and middle-tier business objects used by applications, tools, languages, or Internet browsers.
In This Section What's New in ADO.NET Introduces features that are new in ADO.NET. ADO.NET Overview Provides an introduction to the design and components of ADO.NET. Entity Framework Describes how to create applications using the Entity Framework. Securing ADO.NET Applications Describes secure coding practices when using ADO.NET. Data Type Mappings in ADO.NET Describes data type mappings between .NET Framework data types and the .NET Framework data providers. See also. ADO.NET Entity Framework. Working with ObjectSet. In versions starting with .NET Framework version 4, you can use the following methods defined on ObjectSet instead of the equivalent ones defined on ObjectContext: For example, in .NET Framework 4, use the following code: using (AdventureWorksEntities context = new AdventureWorksEntities()) // Add the new object to the context. context.Products.AddObject(newProduct); In .NET Framework 3.5 SP1, use the following code: context.AddObject("Products", newProduct); The following example demonstrates how to use a non-typed ObjectContext to create an ObjectSet instance. ' Create the ObjectContext. // Create the ObjectContext.
For examples of the testability improvements in the .NET Framework version 4, see the following blog posts: ADO.NET team blog and Julie Lerman's blog. Concepts. Pluralization - Entity Framework Design. Unfortunately in the current version of the Entity Framework, which ships in .NET 3.5 SP1, we don't make any attempt to Singularize or Pluralize names when reverse engineering a model from the database. So if, for example, your database has a table called Orders you will get an EntityType called Orders too, which clearly doesn't make for the most read-able code: Orders order = new Orders(); //?
Why not just Order ? LINQ to SQL does a better job here, because it ships with simple but effective pluralization and singuralization services, that for the most part produces names you would expect. Unfortunately the lack of a similar feature in the Entity Framework, means that generally the first thing you do after you've reverse engineered a model with the Entity Framework is fix-up all the silly names. Now from the perspective of someone who delivers plenty of Entity Framework demos, this is quite embarrassing! Solution: In the next version we have added basic pluralization support. If (mapping ! Entity Data Model. The Entity Data Model (EDM) is a set of concepts that describe the structure of data, regardless of its stored form.
The EDM borrows from the Entity-Relationship Model described by Peter Chen in 1976, but it also builds on the Entity-Relationship Model and extends its traditional uses. The EDM addresses the challenges that arise from having data stored in many forms. For example, consider a business that stores data in relational databases, text files, XML files, spreadsheets, and reports. This presents significant challenges in data modeling, application design, and data access.
When designing a data-oriented application, the challenge is to write efficient and maintainable code without sacrificing efficient data access, storage, and scalability. A conceptual model is a specific representation of the structure of data as entities and relationships, and is generally defined in a domain-specific language (DSL) that implements the concepts of the EDM. In This Section association end facet.