ADO.NET team blog : Providers

New features in Entity Framework impacting providers

dpblogs — Thu, 22 Oct 2009 19:31:10 GMT

Providers for Entity Framework 3.5 will work unmodified against Entity Framework 4.0. Also, most of the features and improvements introduced in Entity Framework 4.0 will just work against an Entity Framework 3.5 provider. However, there are several features that require provider changes to be enabled. Below is a list of these features along with short description of the changes required to enable them.

New features in Entity Framework Runtime impacting providers

New EDM (Canonical) Functions

In Entity Framework 3.5 there is a set of EDM (canonical) functions, which are defined by the Entity Framework and should be supported by all store providers. In Entity Framework 4.0 we are expanding that set by adding a number of new string, aggregate, mathematical, and date/time functions. Providers would need to add support for these new functions, listed below.

Date/Time functions

CreateDateTime(year, month, day, hour, minute, second)

CreateDateTimeOffset(year, month, day, hour, minute, second, tzoffset)

CreateTime(hour, minute, second)

DayOfYear(expression)

TruncateTime(expression)

AddYears(expression, number)

AddMonths(expression, number)

AddDays(expression, number)

AddHours(expression, number)

AddMinutes(expression, number)

AddSeconds(expression, number)

AddMilliseconds(expression, number)

AddMicroseconds(expression, number)

AddNanoseconds(expression, number)

DiffYears(startExpression, endExpression)

DiffMonths(startExpression, endExpression)

DiffDays(startExpression, endExpression)

DiffHours(startExpression, endExpression)

DiffMinutes(startExpression, endExpression)

DiffSeconds(startExpression, endExpression)

DiffMilliseconds(startExpression, endExpression)

DiffMicroseconds(startExpression, endExpression)

DiffNanoseconds(startExpression, endExpression)

Math Functions

Power(value, exponent)

Truncate(value, digits)

Round(value, digits)

Aggregate functions

StDevP(expression)

Var (expression)

VarP (expression)

String functions

Contains(string, target)

StartsWith(string, target)

EndsWith(string, target)

Exposing provider functions in LINQ To Entities ()

Entity Framework 3.5 customers preferring to write their queries using LINQ often hit a limitation on the range of functions and query patterns supported in LINQ to Entities. To address that issue, we are providing an extensibility mechanism that can be used to map CLR methods to provider and to EDM functions.

The basis of the extensibility mechanism is a new method-level attribute that carry function mapping information. Here is the basic signature of the attribute’s constructor:

public EdmFunctionAttribute(string namespaceName, string functionName)

The namespaceName parameter indicates the namespace for the function in metadata (i.e. “EDM” or “SQLSERVER”, or other store provider namespace). The functionName parameter takes the name of the function itself.

We encourage providers to expose classes that represent their store functions, so that when their provider is used they are readily available via LINQ to Entities. Here are some recommendations with regards to which functions to expose and how:

Which functions to expose?

These that provide functionality not already provided via the base class library functions supported by LINQ to Entities or the EDM functions.

Overloads – Provide enough for pleasant user experience

Specify the scalar arguments and return types as nullable
Provide overloads for nullable and non-nullable collection element for collection arguments

Proxies Implementation

Trigger direct evaluation over the input ObjectQuery for methods taking collection arguments
Throw NotSupportedException in all other cases

Example:

[EdmFunction(“SampleSqlServer", "CHECKSUM_AGG")] 
        public static Int32? ChecksumAggregate( IEnumerable<Int32> arg)  { 
            ObjectQuery<Int32> objectQuerySource = arg as ObjectQuery<Int32>; 
            if (objectQuerySource != null)  { 
                return ((IQueryable)objectQuerySource).Provider
                      .Execute<Int32?>(Expression.Call((MethodInfo)MethodInfo
                        .GetCurrentMethod(),Expression.Constant(arg))); 
            } 
     throw new NotSupportedException("This function can only be invoked from LINQ 
                            to Entities."); 
        } 
         [EdmFunction(“SampleSqlServer", "CHECKSUM_AGG")]
         public static Int32? ChecksumAggregate( IEnumerable<Int32?> arg)  { 
        { …. }

Translating String.StartsWith, String.EndsWith and String.Contains to LIKE in LINQ to Entities

In Entity Framework 3.5, in LINQ to Entities we provided support for the String.StartsWith, String.EndsWith and String.Contains and we translated them to canonical functions in the following way:

Boolean String.Contains(String value) -> IndexOf(this, value) > 0

Boolean String.EndsWith(String value) -> Right(this, length(value)) = value

Boolean String.StartsWith(String value) -> IndexOf(this, value) = 1

However, due to the fact that these translations result in inability to utilize indexes on the tested string on some providers and that users found the resulting SQL more difficult to read, we are providing an option to translate these into DbLikeExpression, i.e:

Boolean String.Contains(String value) -> DbLikeExpression(this, ‘%’ + value’ + ‘%’, escapeCharacter)

Boolean String.EndsWith(String value) -> DbLikeExpression(this, ‘%’ + value’, escapeCharacter)

Boolean String.StartsWith(String value) -> DbLikeExpression(this, value’ + ‘%’’, escapeCharacter)

Here, value’ is the equivalent of value but with the wildcard characters and the escape character escaped, and escapeCharacter is the escape character. This translation only happens if value is a constant or a parameter.

Because different providers may have different wildcard characters, in order for this translation to happen provider writers need to override and provide implementations of the following methods that have been introduced in DbProviderManifest:

public virtual bool SupportsEscapingLikeArgument(out char escapeCharacter)

and

public virtual string EscapeLikeArgument(string argument)

The default implementation of SupportsEscapingLikeArgument returns false, thus if provider writers choose to not override these methods, they will still continue to get the old translations of these functions.

Please note that this feature is not any public release yet, but it will be available in .NET 4.0.

New Features in Entity Designer Impacting Providers

Model First

In Visual Studio 2010 the designer can generate mappings, storage model, and database DDL from a conceptual model. This feature is called “Model First.” In order to make this feature highly customizable, it is implemented using a Workflow Foundation (WF) workflow that users can replace. The workflow contains two activities: One which generates MSL and SSDL, and another which generates DDL.

DDL generation is done by a T4 template which processes the SSDL generated by the previous workflow activity. Providers who wish to allow users to generate DDL for databases other than SQL Server will need to install a T4 DDL generation template in:

%localappdata%\Microsoft\[AppId]\10.0\Extensions\Microsoft\Entity Framework Tools\DBGen

Where [AppId] signifies either VisualStudio, VBExpress, VCSExpress, or VNSExpress depending on what SKU the user is using at the moment. Note that when searching for templates, the Entity Framework Designer does not do recursive searches.
Templates from this path have “(User)” post-pended to their name.

For reference, built-in templates are installed in:

%programFiles%\Microsoft Visual Studio 10.0\Common7\IDE\Extensions\Microsoft\Entity Framework Tools\DBGen

Templates from this path have “(VS)” post-pended to their name.

Here is a screenshot. In this case, a template called “CustomDDL.tt” was added to the “(User)” path referenced above. (In the case of this specific machine, that path was D:\Documents and Settings\SQLCL02\Local Settings\Application Data\Microsoft\VisualStudio\10.0\Extensions\Microsoft\Entity Framework Tools\DBGen)

The same rules also apply to workflows. In this screenshot, we added a workflow called “CustomStrategy.xaml” to the “(User)” directory:

In both cases, there is no need to restart VS, as the templates and workflows show up immediately.

Please note that this feature is not any public release yet, but it will be available in Visual Studio 2010.

Thank you!

Kati Iceva
Software Development Engineer, Entity Framework

Noam Ben-Ami
Program Manager, Entity Designer

Entity Framework Provider for Synergy DBMS

dpblogs — Wed, 01 Jul 2009 20:08:00 GMT

It is my pleasure to announce that Synergex has released their Synergy/DE Data Provider for .NET with support for the Entity Framework. The Synergy/DE Data Provider for .NET enables developers to access Synergy DBMS databases from .NET applications and Visual Studio 2008 and to take advantage of the Entity Framework and LINQ.

For more information, see the Synergex announcement page about the release here. Congratulations to everyone at Synergex who contributed to the release!

Enjoy!

Elisa Flasko
Program Manager, Data Programmability

ADO.NET Entity Framework Provider for Firebird RTM Now Available

dpblogs — Mon, 01 Jun 2009 19:29:00 GMT

Firebird recently announced the RTM of FirebirdClient 2.5. This new release now provides full support for the Entity Framework. To learn more about FirebirdClient 2.5 check out Jiri’s blog at http://blog.vyvojar.cz/jirka/archive/2009/05/22/ann-firebirdclient-2-5-final-released.aspx or access the download page at http://www.firebirdsql.org/index.php?op=files&id=netprovider

Elisa Flasko
Program Manager, Data Programmability

Entity Framework-Enabled Providers Lists

dpblogs — Mon, 26 Jan 2009 23:05:00 GMT

I love posting announcements to the blog to let people know about the latest and greatest information about Entity Framework-enabled ADO.NET providers. Blogs are perfect for announcements like that, but they're not as handy for providing an overview about the available Entity Framework-enabled providers.

To help customers quickly and easily see what Entity Framework-enabled providers are available, released providers are listed on the main Entity Framework page here. We also have a separate page that lists all publicly available providers, including pre-released providers here.

We'll continue to post announcements about provider availability to the team blog. The corresponding entries will appear on the provider list pages within a couple days, since those changes require more time to format and review.

David Sceppa
ADO.NET Program Manager

OpenLink Releases Their Virtuoso ADO.NET Entity Framework Provider

dpblogs — Tue, 13 Jan 2009 04:20:00 GMT

It is my pleasure to announce that OpenLink Software has released their Virtuoso ADO.NET Entity Framework provider - an ADO.NET 3.5 data provider compatible with Visual Studio 2008 and Entity Frameworks, that provides access to native Virtuoso data (SQL, XML, and RDF) in addition to any Virtuoso Linked Tables from external ODBC and JDBC accessible data sources. Known-compatible external data sources include Oracle (versions 7.x to 11.x), Microsoft SQL Server (6.x to 2005), IBM DB2 , Sybase (4.2 to 12.x+), IBM Informix (5.x to 11.x), Ingres (6.4 to 9.x), Progress (7.x to 10.x), MySQL, PostgreSQL, and Firebird.

For more information, see the OpenLink announcement page about the release here. Congratulations to everyone at OpenLink who contributed to the release!

Enjoy!

David Sceppa
ADO.NET Program Manager

Beta of Firebird ADO.NET Provider with Entity Framework Support Available

dpblogs — Tue, 13 Jan 2009 03:52:00 GMT

I'm pleased to announce that a beta of the Firebird ADO.NET provider with Entity Framework support is now available. Congratulations to Jiří Činčura and to everyone else who has worked on this project so far!

For more information, please see Jiří's blog post here or access the download page for the provider here.

Enjoy!

David Sceppa
ADO.NET Program Manager

IBM's ADO.NET Provider Supports the Entity Framework!

dpblogs — Thu, 11 Dec 2008 03:57:00 GMT

Time for another update on Entity Framework-enabled ADO.NET providers.

It is my pleasure to announce that IBM has added Entity Framework support to their ADO.NET provider. The provider supports DB2, Informix and U2 databases. For more information on the specific versions of the IBM data servers supported, see this page on the IBM web site.

Congratulations to everyone at IBM who contributed to the release, and a special thanks to Brent Gross and Praveen Ghantasala for all of the feedback they provided back to the Entity Framework team!

Enjoy!

David Sceppa
ADO.NET Program Manager

Sybase's SQL Anywhere ADO.NET Provider Supports the ADO.NET Entity Framework!

dpblogs — Tue, 21 Oct 2008 21:13:00 GMT

Another Entity Framework-enabled ADO.NET providers post! Woohoo!

It is my pleasure to announce that as part of the release of SQL Anywhere 11, Sybase iAnywhere has added Entity Framework support to their ADO.NET provider. For more information on the SQL Anywhere 11 release, please see the following announcement on the Sybase web site:

http://www.sybase.com/detail?id=1057559

Congratulations to everyone else at Sybase who contributed to the release!

Enjoy!

David Sceppa

ADO.NET Program Manager

Npgsql's ADO.NET Provider for PostgreSQL Supports the ADO.NET Entity Framework!

dpblogs — Wed, 15 Oct 2008 00:40:00 GMT

I always enjoy making announcements regarding external providers releasing their Entity Framework-enabled ADO.NET providers.

It is my pleasure to announce that Npgsql has released a version 2.0 of their ADO.NET provider for PostgreSQL, which includes support for the Entity Framework. For more information, see the following announcement on the PgFoundry web site:

http://pgfoundry.org/frs/shownotes.php?release_id=1230

Congratulations to Josh Cooley and everyone else on the Npgsql team who contributed to the release!

Enjoy!

David Sceppa

ADO.NET Program Manager

Devart's New Providers Support the ADO.NET Entity Framework!

dpblogs — Fri, 05 Sep 2008 21:05:00 GMT

It is my pleasure to announce the first (to the best of my knowledge) external providers to support the ADO.NET Entity Framework!

Devart (formerly Core Lab) has released a new version of their ADO.NET providers, which includes support for the Entity Framework. For more information, see the following announcement on Devart's web site. Congratulations to the folks at Devart!

http://devart.com/news/2008/directs475.html

With the release of Devart's providers, developers can now acess their Oracle, MySQL and PostgreSQL databases via the Entity Framework. I've downloaded and used their OraDirect.NET provider to successfully run sample queries against an Oracle database using both LINQ and Entity SQL.

Enjoy!

David Sceppa

ADO.NET Program Manager

New sample provider demonstrates Oracle connectivity

dpblogs — Tue, 24 Jun 2008 20:08:00 GMT

As noted on Jaroslaw Kowalski's blog, we have released a new flavor of the ADO.NET Entity Framework sample provider. You can access the Oracle flavor of the sample provider on the Code Gallery site here.

The new sample wraps System.Data.OracleClient instead of System.Data.SqlClient, demonstrating Oracle connectivity from the Entity Framework. We chose to build this second flavor of the sample provider using OracleClient to help the provider writer community as well as to investigate issues that third party provider writers might encounter. As noted in the readme for the OracleClient sample provider, we've addressed many of those issues within the Entity Framework in more recent builds.

The OracleClient flavor of the sample provider also demonstrates some key concepts we wanted to convey to other provider writers such as non-default type mappings, data type coercion in the reader, and canonical functions. For more information on these topics, see Jarek's blog post.

As with the SqlClient flavor of the sample provider, we've chosen a license agreement that we believe will allow most provider writers to leverage the code in the sample to give them a running head start.

Enjoy!

David Sceppa

ADO.NET Program Manager

Entity Framework Provider Updates

dpblogs — Thu, 05 Jun 2008 22:31:00 GMT

Greetings from TechEd!

We've updated the ADO.NET Entity Framework Sample Provider for .NET 3.5 SP1 Beta and posted it at the MSDN Code Gallery site. You can download the sample provider here: http://code.msdn.microsoft.com/EFSampleProvider

Yesterday we held a chalk talk session with many of our provider writer partners. The theater was so full with attendees that we ran out of seats. Representatives from DataDirect, IBM, Oracle and Sybase were in attendance. Over the course of the chalk talk, we addressed a number of general questions before attendees spoke directly with the representatives from the various provider writers. DataDirect announced that they will release an update to their Oracle ADO.NET provider to support the Entity Framework in Q3 of 2008. Both IBM and Sybase demonstrated their provider's accessing their data stores via the Entity Framework.

Reggie Burnett, the lead developer for the MySQL ADO.NET provider, was unable to attend but asked me pass along the following information:

"In the next few days we will be making available a pre-release of version 5.3 with preliminary support for the entity framework as it is found in Visual Studio 2008 SP1 beta. We are firmly committed to supporting this technology and are actively working on it."

David Sceppa

ADO.NET Program Manager

Recent ADO.NET Entity Framework provider news - Demos and downloads

dpblogs — Wed, 07 May 2008 08:23:00 GMT

Here are a few quick announcements about ADO.NET providers supporting the Entity Framework. Enjoy!

Core Lab (Connectivity to Multiple Data Stores)

Core Lab was the first ADO.NET provider writer to support Beta 3 of the Entity Framework. Their provider includes connectivity to Oracle, MySQL, PostgreSQL and SQLite databases. For more information, see the announcement on the following pages: http://crlab.com/news/2007/directs430.html and http://crlab.com/news/2008/dcsqlite100.html.

IBM

IBM has released a public beta for their ADO.NET provider that works with Beta 3 of the Entity Framework. For more information, see the announcement on the following page: http://www-128.ibm.com/developerworks/forums/thread.jspa?threadID=203893. IBM also demonstrated their provider in an end-to-end application building scenario using the Entity Framework designer at recent VS Live conference in San Francisco.

MySQL

At the recent MySQL conference in Santa Clara, Reggie Burnett and I co-presented a session talking about MySQL, LINQ and the ADO.NET Entity Framework. As part of the session, we demonstrated using LINQ, Entity SQL and ADO.NET Data Services to access a MySQL database using Beta 3 of the Entity Framework.

Note: Big thanks to Reggie for helping to make this demo work even after injuring his knee. Get well soon.

Npgsql (PostgreSQL connectivity)

Npgsql has released a beta of their PostgreSQL ADO.NET provider that works with Beta 3 of the Entity Framework. You can download the provider at the following page: http://pgfoundry.org/frs/download.php/1730/Npgsql2.0beta3-bin-EntityFrameworkBeta3.zip. For more information on the release, please see the following page: http://pgfoundry.org/forum/forum.php?forum_id=1307.

David Sceppa

ADO.NET Program Manager

Sample ADO.NET Entity Framework Provider - Beta 3

dpblogs — Tue, 18 Dec 2007 04:37:00 GMT

We've updated the sample provider to work with Beta 3 of the ADO.NET Entity Framework. The sample provider is available for download as an attachment to this blog post.

The sample provider has undergone some minor changes in moving from Beta 2 to Beta 3. The biggest such in the sample provider is due to changes in the provider manifest. To help provider writers better understand how provider manifests are used in Beta 3, we've included the provider manifest spec along with the sample provider.

As with previous builds, the sample provider wraps System.Data.SqlClient and demonstrates the functionality a provider needs to add in order to support the ADO.NET Entity Framework. The solution that contains the sample provider also includes a modified version of the Entity Framework Query Samples project. The modified project uses the sample provider rather than System.Data.SqlClient.

You'll also find a new project in the solution - ExtendedProvider. This project leverages the sample provider and the Data Designer Extensibility (DDEX) that's part of Visual Studio 2008 to demonstrate how to make an ADO.NET provider available through the various Visual Studio designers, including the ADO.NET Entity Framework Designer.

If you're writing an ADO.NET provider for the Entity Framework and you're not already in touch with me, please drop me a line at David (dot) Sceppa (at) microsoft (dot) com. Enjoy!

David Sceppa

ADO.NET Program Manager

Microsoft Corporation

Sample ADO.NET Entity Framework Provider - Beta 2

dpblogs — Sat, 22 Sep 2007 03:31:00 GMT

We've updated the sample provider to work with Beta 2 of the ADO.NET Entity Framework. The sample provider is available here.

The sample provider has undergone some minor changes in moving from Beta 1 to Beta 2.

The DbProviderServices class has been enhanced to support returning the mapping file that the EdmGen.exe command-line tool uses to retrieve schema information from the database. This new approach leverages the Entity Framework's mapping functionality and the provider's SQL-gen layer to map conceptual table, view, column, etc. schema information to the database's actual system tables. The end result is that EdmGen.exe can retrieve database schema information in a provider agnostic fasion.

Also, the SQL generation layer within the sample provider has been enhanced to support the new canonical function capabilities added in Beta 2 of the ADO.NET Entity Framework.

If you're writing an ADO.NET provider for Orcas and you're not already in touch with me, please drop me a line at David (dot) Sceppa (at) microsoft (dot) com. Enjoy!