New CTP for LINQ

What’s new?

LINQ:

• IQueryable<T> enables pluggable query processors.
  • ToQueryable provides a way to get an expression tree from an IEnumerable<T> so that a pluggable query processor can optimize and execute it
  • Expression.Compile enables compilation of an expression tree for in-memory execution
• Join support has been added: Join operator provides inner equi-join and a powerful GroupJoin operator retains the hierarchical structure while providing additional outer-join like capabilities
• A family of additional operators: Single, SingleOrDefault, Last, LastOrDefault, ElementAt, ElementAtOrDefault

C# Language:

• Query expressions now provide:
  • Join syntax for using Join and GroupJoin
  • Let clause for declaring temporary variables in query expression
• Lambda statement blocks are enabled in addition to lambda expressions

C# IDE:

• Support for copy-pasting XML for simplified use of XLinq

DLinq:

• A graphical designer has been added for generating mapped classes. This designer requires Visual Studio 2005 Professional Edition or above.
• Inheritance
• Multi-tier entity support
• Enhanced support for stored procedures and user-defined functions
• Improved concurrency conflict resolution
• Remote / local EntitySet
• XML mapping file
• Additional .NET functions

XLinq

• Supports annotations, an extensibility point for user data
• Improved support for XML mixed content
• Support for streaming output

LINQ over DataSet:

• Adds new LINQ component to query DataTables – implements the LINQ query pattern including join
• Adds DataSet-specific operators like DistinctRows, UnionRows for traditional relational set operations
• Provides ToDataTable() operator to get a DataTable from a sequence

Miscellaneous:

• Web project template that allows prototype C# compiler to be used in web projects
• WinForms and ASP.NET databinding samples
• An expression tree visualizer for better inspection of expression trees
• A DLinq query visualizer for better debugging experience

C# Support:

The installer sets up several LINQ project templates (LINQ Windows Application, LINQ Web Site, LINQ Console Application, LINQ WinFX Application and LINQ Library) that you can use to create your own C# 3.0 projects using LINQ.

IDE Support (for Visual Studio 2005/C# 2005 Express):

Project LINQ relies on several changes to the C# language.  C# 3.0 contains new keywords and syntax that are not considered valid by the Visual Studio 2005 IDE.  The result is that editing LINQ-enabled C# code can be difficult: For example, there is no IntelliSense™ support for the new language features, errors are incorrectly reported in the output window, and the code editor underlines valid C# 3.0 code with red squiggles.  A modified C# language service has been created to help alleviate these problems in the IDE, to provide the new keywords in the completion list, and to provide extension methods in IntelliSense™.

While this preliminary IDE support greatly enhances the editing experience when writing C# 3.0 code in VS 2005, the language service and compiler are still very much in an alpha phase.  In the event of a compiler error, many more errors may be reported than are actually present.  If you see a large number of errors when building C# 3.0 code, fix the top error in the error list first and build after each fix.

Follow these steps to enable LINQ IDE support for Visual Studio 2005 and Visual C# 2005 Express: 

1. First, verify that you are running the release version of Visual Studio 2005 or Visual C# 2005 Express.  The language service that will be installed only works with the English version of VS 2005/C# 2005 Express and may cause severe problems if installed on earlier versions.  You can verify your version by selecting Help\About in Visual Studio 2005. 
2. Shut down any running instances of Visual Studio.
3. Open the \bin folder under the LINQ preview installation directory and run “Install C# IDE Support”.
4. Start VS 2005/C# 2005 Express.

Follow these steps to restore your original VS 2005/C# 2005 Express language service:

1. Shut down any running instances of Visual Studio.
2. Open the \bin folder under the LINQ preview installation directory and run “Uninstall C# IDE Support”.
3. Start VS 2005/C# 2005 Express.

Visual Basic Support:

If you also have Visual Basic installed on your machine, the files for preview for Visual Basic are installed. The readme for Visual Basic can be found here. The preview files for Visual Basic are not installed if you do not have Visual Basic installed as a part of Microsoft Visual Studio 2005 or Microsoft Visual Basic Express 2005.