Using SQL JOIN Operation In LinQ/C# Posted on March 30, 2011 Being LinQ an Object Relational Mapper, We can avoid writing sql query in many cases. Where its needed to be written even for simple purpose, we can achieve what we need just by calling linq provided methods with proper parameters.This facilitates to make the code more meaningful and less buggy. Join operations are done in sql for retrieve data from a complex relationship between tables, using linq we can avoid this complexity in most of the cases, therefore no more brainstorming for writing big/complex queries anymore. In this tutorial, I will give some examples along with code samples for performing join operations with help of linq to sql easily and quickly. As this article focus completely on join operation, if you are a beginner linq programmer, consider my previous tutorial on getting started with linq to sql.
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By: Sherlee Dizon Updated: 2011-10-14 Comments (6) Related: More Language Integrated Query LINQ Problem. In my project I need to retrieve and join data from two different SQL Server databases on two different SQL Server instances. The data retrieval can only be done via the existing stored procedures that have been created in these databases.
There are several areas of .NET of interest to the Database Programmers, including the topics about data infrastructures in the .NET framework. This article explains ADO.NET and Entity Framework as the two main options for accessing and manipulating data. The concept of LINQ will also be discussed here.
Microsoft creates and launches a new data framework and tool every few years. While doing so, they also update or enhance the existing frameworks. As a result of their ongoing efforts, it’s sometimes confusing when understanding and choosing a data access strategy for our projects.
ADO.NET
ADO.NET is the oldest Microsoft data access framework. It shipped in the original release of .NET Framework and has proven to be stable and dependable. ADO.NET is a set of libraries that supports interactions with many data sources.
ADO.NET is cross-platform compatible, and we can use it with nearly all major database implementations such as SQL Server, Oracle, MS Access, and ODBC. When we use commands like INSERT and UPDATE, it opens a connection to the database, executes the command, and closes the connection as soon as possible.
The ADO.NET framework includes a System.Data namespace with various objects for data manipulation. Many classes form the core foundation of ADO.NET. Here are some of them:
Figure 1. ADO.NET infrastructure
ADO.NET supports the disconnected model, which is essential for performance. We can work with a disconnected copy of the database in memory, and then save the changes to the database. This feature is vital if we’re working with a network shared database because traffic is expensive.
Entity Framework (or ADO.NET Entity Framework)
Entity Framework is the Microsoft version of Object-Relational Mapper (ORM). It’s important to note that Entity Framework is built on ADO.NET classes. Entity Framework is also called ADO.NET Entity Framework.
As developers work with strongly typed .NET objects called entities, there was a big gap between the object models used in the Object-Oriented Programming (OOP) and the data storage, which is in a relational model. Much code was needed to deal with this gap. ORM was created to resolve this issue. It is a technique for converting data stored in a relational database to domain-specific classes.
Entity Framework offers many benefits compared to previous technology. One of its advantages is the excellent tooling support where we can build and maintain data access in a much shorter time. We can focus on solving business problems without worrying about the underlying data storage.
LINQ
Language Integrated Query (LINQ) is a set of technologies that integrates query capabilities into .NET languages (C# and VB.NET). LINQ is released as a major part of .NET Framework 3.5 in 2007. LINQ offers a consistent way to query and manipulate data across different data sources.
Here are different types of LINQ; each one is optimized for querying a particular type of data.
Figure 2. LINQ Providers
ADO.NET vs. Entity Framework vs. LINQ
Here’s a summary of ADO.NET, Entity Framework, and LINQ, presented in one table.
Table 1. ADO.NET vs. Entity Framework vs. LINQ
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