Jaroslaw Kowalski : EFSampleProvider

Using EF Oracle Sample Provider with EDM Designer

jkowalski — Fri, 24 Oct 2008 20:24:49 GMT

Many people are asking if it is possible to use EFOracleProvider with EDM Designer in Visual Studio 2008 SP1. The answer is yes, but because the sample doesn't include a DDEX provider required for VS integration, there are certain steps that have to be run manually.

I've compiled a step-by-step guide for those interested in trying this out (this assumes NorthwindEF sample database installed according to instructions included with the sample, but it should be straightforward to adjust it to your own setup)

PART 1 : INSTALLING ORACLE SAMPLE PROVIDER

1. Download and unzip EFOracleSampleProvider.zip from http://code.msdn.com/EFOracleProvider

2. Follow instructions in the README.txt to set up a sample database.

3. Open elevated Visual Studio instance. Build the sample project.

4. Open elevated command prompt and open machine.config using notepad:
notepad %WINDIR%\Microsoft.NET\Framework\v2.0.50727\config\machine.config

5. Find <DbProviderFactories> section and add EFOracleProvider entry:

<add name="EF Oracle Data Provider" invariant="EFOracleProvider" 
     description="EF Provider for Oracle testing" 
     type="EFOracleProvider.EFOracleProviderFactory, EFOracleProvider, Version=1.0.0.0, Culture=neutral, PublicKeyToken=def642f226e0e59b"/>

6. The completed system.data section has to look similar to this:

<system.data>
  <DbProviderFactories>
    <add name="Odbc Data Provider" invariant="System.Data.Odbc" description=".Net Framework Data Provider for Odbc" type="System.Data.Odbc.OdbcFactory, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
    <add name="OleDb Data Provider" invariant="System.Data.OleDb" description=".Net Framework Data Provider for OleDb" type="System.Data.OleDb.OleDbFactory, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
    <add name="OracleClient Data Provider" invariant="System.Data.OracleClient" description=".Net Framework Data Provider for Oracle" type="System.Data.OracleClient.OracleClientFactory, System.Data.OracleClient, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
    <add name="SqlClient Data Provider" invariant="System.Data.SqlClient" description=".Net Framework Data Provider for SqlServer" type="System.Data.SqlClient.SqlClientFactory, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
    <add name="EF Oracle Data Provider" invariant="EFOracleProvider" description="EF Provider for Oracle testing" type="EFOracleProvider.EFOracleProviderFactory, EFOracleProvider, Version=1.0.0.0, Culture=neutral, PublicKeyToken=def642f226e0e59b"/>
    <add name="Microsoft SQL Server Compact Data Provider" invariant="System.Data.SqlServerCe.3.5" description=".NET Framework Data Provider for Microsoft SQL Server Compact" type="System.Data.SqlServerCe.SqlCeProviderFactory, System.Data.SqlServerCe, Version=3.5.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"/>
  </DbProviderFactories>
</system.data>

PART 2: GENERATING MODEL FROM ORACLE DATABASE

7. Create a new project in VS. For simplicity let's create a console application

8. Open elevated command prompt. Enter the directory that contains the newly created project and run the following command:

%WINDIR%\Microsoft.NET\Framework\v3.5\edmgen.exe /provider:EFOracleProvider /mode:fullgeneration 
      /connectionstring:"data source=XE;user id=edmuser;password=123456" /project:NorthwindEFModel

The output should be:

Microsoft (R) EdmGen version 3.5.0.0
Copyright (C) 2008 Microsoft Corporation. All rights reserved.

Loading database information...
warning 6005: The data type 'timestamp(9)' is not supported, the column 'OrderDate' in table 'dbo.Orders' was excluded.
warning 6005: The data type 'timestamp(3)' is not supported, the column 'RequiredDate' in table 'dbo.Orders' was excluded.
Writing ssdl file...
Creating conceptual layer from storage layer...
Writing msl file...
Writing csdl file...
Writing object layer file...
Writing views file...

Generation Complete -- 0 errors, 2 warnings

9. This will create a bunch of NorthwindEFModel.* files for you.

10. Open Northwind.ssdl file in a text editor and replace all instances of Schema="dbo" with empty string (this is needed because tables in the sample Oracle database don't use a schema)

11. In order to use generated model in the EF Ddesigner, we have to create NorthwindEFModel.edmx file. This can be done manually (just copy/paste contents of individual files into an empty EDMX as indicated by the comments) or by using EdmGen2 tool from Code Gallery:

C:\Path\To\EdmGen2.exe /toedmx NorthwindEFModel.csdl NorthwindEFModel.ssdl NorthwindEFModel.msl

12. This will create NorthwindEFModel.edmx, which we can add to the project in VS.

13. At this point you can now delete the following files generated by EdmGen.exe, which won't be necessary:

NorthwindEFModel.csdl
NorthwindEFModel.ssdl
NorthwindEFModel.msl
NorthwindEFModel.ObjectLayer.cs
NorthwindEFModel.Views.cs

PART 3: TESTING GENERATED MODEL

14. The only remaining thing to do is to add App.config file with connection string for our Oracle database:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="NorthwindEFModelContext" 
         connectionString="provider=EFOracleProvider;
                           metadata=res://*/NorthwindEFModel.csdl|res://*/NorthwindEFModel.ssdl|res://*/NorthwindEFModel.msl;
                           Provider Connection String='data source=XE;user id=edmuser;password=123456'" 
         providerName="System.Data.EntityClient" />
  </connectionStrings>
</configuration>

15. We can now try out our model by running a sample LINQ to Entities query:

using (NorthwindEFModelContext context = new NorthwindEFModelContext())
{
    foreach (var c in context.Customers.Where(c=>c.City == "Seattle"))
    {
        Console.WriteLine(c.CompanyName);
    }
}

Sample Entity Framework Provider for Oracle

jkowalski — Tue, 24 Jun 2008 01:54:05 GMT

I wanted to let you know that we have just released Sample Entity Framework Provider for Oracle on MSDN Code Gallery.

http://code.msdn.com/EFOracleProvider

The provider is implemented using essentially the same technique as EFSampleProvider, but targets System.Data.OracleClient instead of System.Data.SqlClient. The provider is compatible with Visual Studio SP1 Beta and the code is released under Microsoft Public License (Ms-PL).

There are three notable features of this provider:

Non-default type mappings. In EFOracleProviderManifest we are supporting non-default type mappings:
- EFOracle.number(1,0) maps to Edm.Boolean
- EFOracle.number(5,0) maps to Edm.Int16
- EFOracle.number(11,0) maps to Edm.Int32
- EFOracle.raw(16) maps to Edm.Guid

Here's the interesting piece of code taken from EFOracleProviderManifest.GetEdmType() that does it. It looks at facets attached to the given store type and translates certain combinations of them into mentioned EDM types.

case "number":
    {
        byte precision;
        byte scale;

        if (MetadataHelpers.TryGetPrecision(storeType, out precision) &&
            MetadataHelpers.TryGetScale(storeType, out scale))
        {
            if (precision == 1 && scale == 0)
                return TypeUsage.CreateDefaultTypeUsage(PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.Boolean));

            if (precision == 5 && scale == 0)
                return TypeUsage.CreateDefaultTypeUsage(PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.Int16));

            if (precision == 11 && scale == 0)
                return TypeUsage.CreateDefaultTypeUsage(PrimitiveType.GetEdmPrimitiveType(PrimitiveTypeKind.Int32));

            return TypeUsage.CreateDecimalTypeUsage(edmPrimitiveType, precision, scale);
        }
        else
        {
            return TypeUsage.CreateDecimalTypeUsage(edmPrimitiveType);
        }
    }

Data type coercion in the data reader. Data provider analyzes Canonical Query Tree (CQT) and remembers expected CLR types for each result column ordinal. Whenever this data type is different from the data returned by wrapped OracleDataReader, the value is coerced using Convert.ChangeType().

The code below extracts ExpectedColumnTypes from the canonical query tree:

// Set expected column types for DbQueryCommandTree
DbQueryCommandTree queryTree = commandTree as DbQueryCommandTree;
if (queryTree != null)
{
    DbProjectExpression projectExpression = queryTree.Query as DbProjectExpression;
    if (projectExpression != null)
    {
        EdmType resultsType = projectExpression.Projection.ResultType.EdmType;

        StructuralType resultsAsStructuralType = resultsType as StructuralType;
        if (resultsAsStructuralType != null)
        {
            command.ExpectedColumnTypes = new PrimitiveType[resultsAsStructuralType.Members.Count];

            for (int ordinal = 0; ordinal < resultsAsStructuralType.Members.Count; ordinal++)
            {
                EdmMember member = resultsAsStructuralType.Members[ordinal];
                PrimitiveType primitiveType = member.TypeUsage.EdmType as PrimitiveType;
                command.ExpectedColumnTypes[ordinal] = primitiveType;
            }
        }
    }
}

// Set expected column types for DbFunctionCommandTree
DbFunctionCommandTree functionTree = commandTree as DbFunctionCommandTree;
if (functionTree != null)
{
    if (functionTree.ResultType != null)
    {
        Debug.Assert(MetadataHelpers.IsCollectionType(functionTree.ResultType.EdmType),
            "Result type of a function is expected to be a collection of RowType or PrimitiveType");

        EdmType elementType = MetadataHelpers.GetElementTypeUsage(functionTree.ResultType).EdmType;

        if (MetadataHelpers.IsRowType(elementType))
        {
            ReadOnlyMetadataCollection<EdmMember> members = ((RowType)elementType).Members;
            command.ExpectedColumnTypes = new PrimitiveType[members.Count];

            for (int ordinal = 0; ordinal < members.Count; ordinal++)
            {
                EdmMember member = members[ordinal];
                PrimitiveType primitiveType = (PrimitiveType)member.TypeUsage.EdmType;
                command.ExpectedColumnTypes[ordinal] = primitiveType;
            }

        }
        else if (MetadataHelpers.IsPrimitiveType(elementType))
        {
            command.ExpectedColumnTypes = new PrimitiveType[1];
            command.ExpectedColumnTypes[0] = (PrimitiveType)elementType;
        }
        else
        {
            Debug.Fail("Result type of a function is expected to be a collection of RowType or PrimitiveType");
        }
    }
}

The provider needs to store this information in the DbCommand and pass down to DbDataReader. In the reader implementation, actual data coercion is done in the following manner:

public partial class EFOracleDataReader : DbDataReader 
{
    private PrimitiveType[] _expectedColumnTypes;

    // ...

    public override DateTime GetDateTime(int ordinal)
    {
        return (DateTime)GetValue(ordinal);
    }

    public override decimal GetDecimal(int ordinal)
    {
        return (decimal)GetValue(ordinal);
    }

    public override object GetValue(int ordinal)
    {
        object rawValue = _oracleReader.GetValue(ordinal);

        if (_expectedColumnTypes != null)
        {
            if (!(rawValue is DBNull) && rawValue.GetType()
                != _expectedColumnTypes[ordinal].ClrEquivalentType)
            {
                rawValue = ChangeType(rawValue, _expectedColumnTypes[ordinal].ClrEquivalentType);
            }
        }
        return rawValue;
    }

    private object ChangeType(object sourceValue, Type targetType)
    {
        if (sourceValue is byte[] && targetType == typeof(Guid))
        {
            return new Guid((byte[])sourceValue);
        }
   
        if (sourceValue is DateTime && targetType == typeof(DateTimeOffset))
        {
            return new DateTimeOffset((DateTime)sourceValue);
        }

        return Convert.ChangeType(sourceValue, targetType, CultureInfo.InvariantCulture);
    }

    // ...
}

Canonical Functions. Most Canonical Functions required by Entity Framework have been implemented using Oracle's built-in functions. In some cases it required some query rewriting, such as when handling Right() canonical function which has no direct Oracle translation and SUBSTR() must be used instead.

private static ISqlFragment HandleCanonicalFunctionRight(SqlGenerator sqlgen, DbFunctionExpression e)
{
    SqlBuilder result = new SqlBuilder();
    result.Append("(CASE WHEN LENGTH(");
    result.Append(e.Arguments[0].Accept(sqlgen));
    result.Append(") >= (");
    result.Append(e.Arguments[1].Accept(sqlgen));
    result.Append(") THEN ");
    result.Append("SUBSTR (");
    result.Append(e.Arguments[0].Accept(sqlgen));
    result.Append(",-(");
    result.Append(e.Arguments[1].Accept(sqlgen));
    result.Append("),");
    result.Append(e.Arguments[1].Accept(sqlgen));
    result.Append(")");
    result.Append(" ELSE ");
    result.Append(e.Arguments[0].Accept(sqlgen));
    result.Append(" END)");
    return result;
}

Let me know if you have any questions about the EFOracleProvider release and EF provider interface in general.

Entity Framework Sample Provider for Visual Studio 2008 SP1 Beta is Online

jkowalski — Tue, 03 Jun 2008 08:48:00 GMT

We have just published an updated Sample ADO.NET Provider for Entity Framework.

Changes in the provider APIs since Beta3 release:

removed DbProviderServices.GetProviderManifest(DbConnection)
added DbProviderServices.GetProviderManifestToken(DbConnection)
completely redesigned CSDL/SSDL/MSL for SchemaInformation
changed the format of the provider manifest XML:
- DefaultValue vs Default
- removed facets from functions
added DbProviderManifest.Token/DbProviderManifest.Provider properties

Provider writers can get the source code from MSDN Code Gallery: http://code.msdn.microsoft.com/EFSampleProvider