Switching between MySQL/SQL Server in EF6

entity-framework-6 mysql sql-server

Question

I have a project that runs on both MySQL and SQL Server. During the last weeks I have managed to "migrate" it from plain old SQL to Entity Framework (using Spring dependency injection too) using a Database-first design based on the existing SQL Server schema.

Now I need to test with MySQL. Even if I used the "appropriate" MySQL configuration, the app will crash on a ClassCastException from MySql.Data.MySqlClient.MySqlConnection to System.Data.SqlClient.SqlConnection

Code:

//Autowired by Spring
public auitool2014Entities DataContext{get;set;}

public IList<News> FindAllValid()
{
    return (from News news in DataContext.news where news.annullata == 0 select news).ToList();
}

Spring definition:

<object id="dataContext" singleton="false" scope="request" type="DiagnosticoSite.Models.auitool2014Entities, Auitool2014" factory-object="dataContextFactory" factory-method="Build" destroy-method="Dispose" ></object>

Spring factory:

public auitool2014Entities Build()
{
    return new auitool2014Entities();
}

Error message (translated from localized)

Unable to cast object of type 'MySql.Data.MySqlClient.MySqlConnection' to type 'System.Data.SqlClient.SqlConnection'.

Following the stack trace:

[InvalidCastException: Unable to cast object of type 'MySql.Data.MySqlClient.MySqlConnection' type 'System.Data.SqlClient.SqlConnection'.]
   System.Data.SqlClient.SqlCommand.set_DbConnection(DbConnection value) +26
   System.Data.Common.DbCommand.set_Connection(DbConnection value) +9
   System.Data.Entity.Internal.InterceptableDbCommand.set_DbConnection(DbConnection value) +41
   System.Data.Common.DbCommand.set_Connection(DbConnection value) +9
   System.Data.Entity.Core.Common.Utils.CommandHelper.SetStoreProviderCommandState(EntityCommand entityCommand, EntityTransaction entityTransaction, DbCommand storeProviderCommand) +123
   System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.PrepareEntityCommandBeforeExecution(EntityCommand entityCommand) +314
   System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +70
   System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlan.Execute(ObjectContext context, ObjectParameterCollection parameterValues) +1283
   System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__6() +185
   System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction(Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) +448
   System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__5() +271
   System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +251
   System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +648
   System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0() +68
   System.Data.Entity.Internal.LazyEnumerator`1.MoveNext() +68
   System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +381
   System.Linq.Enumerable.ToList(IEnumerable`1 source) +58
   DiagnosticoSite.Data.Managers.Spring.NewsManagerImpl.FindAllValid() in d:\Documents\Visual Studio 2013\Projects\Auitool\Auitool2014\Data\Managers\Spring\NewsManagerImpl.cs:16

Following the configuration:

  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6, Version=6.9.5.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>
  <system.data>
    <DbProviderFactories>
      <remove invariant="MySql.Data.MySqlClient" />
      <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.9.5.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />
    </DbProviderFactories>
  </system.data>

I basically changed my connection string to a MySQL connection string

<add name="myConnectionString" connectionString="metadata=res://*/Models.Auitool2014.csdl|res://*/Models.Auitool2014.ssdl|res://*/Models.Auitool2014.msl;provider=Mysql.Data.MysqlClient;provider connection string=&quot;Server=localhost;Database=auitemp;Uid=root;Pwd=root;Allow Zero Datetime=True;CharSet=latin1;Pooling=True;Min Pool Size=5&quot;" providerName="System.Data.EntityClient" />

How can I switch after compilation between the two DBs? I mentioned Spring because my DbContext is request-scoped object that can be easily instantiated through a factory object.

Investigation progress

I found that the stack trace reports the following class involved: System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy. This obviously looks part of the SQL Server package. I need to understand how EF instantiates that. In EF source code I see

var executionStrategy = ExecutionStrategy
                                    ?? DbProviderServices.GetExecutionStrategy(QueryState.ObjectContext.Connection, QueryState.ObjectContext.MetadataWorkspace);

Really, that must be an instance of MySql.Data.entity.EF6.MySqlExecutionStrategy

1
0
1/27/2015 3:44:26 PM

Accepted Answer

Fixed changing EntityFramework's configuration

  <entityFramework codeConfigurationType="MySql.Data.Entity.MySqlEFConfiguration, MySql.Data.Entity.EF6">
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6" />
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>

MySql.Data.Entity.MySqlEFConfiguration is the key. Summarizing, in order to switch from SQL Server to MySQL I have to:

  • Edit the damn connection string
    • Provider attribute is always System.Data.EntityClient
    • Within Connection string, change provider to MySql.Data.MySqlClient
  • Replace entityFramework tag with the above
1
1/27/2015 3:50:32 PM


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