c# Entity Framework EF 4.1 Změna schématu a názvu databáze za běhu

Vlastně jsem na to taky potřeboval řešení. Rychle jsem namíchal roztok, který funguje dobře. Na internetu jsem o tom nenašel mnoho informací, takže si nejsem jistý tím, že "EF 4.1 přichází s lepšími nástroji podpory."

Konkrétní příklad „Změna názvu schématu za běhu – Entity framework“ mi úplně nefungoval, ale s drobnými úpravami jsem to zprovoznil.

Zde je třída DatabaseUtils, která to umí:

internal static class DatabaseUtils
{
    /// <summary>
    /// Builds the connection string for Entity framework.
    /// </summary>
    /// <returns></returns>
    public static EntityConnection BuildConnection(BuildConnectionParams buildConnectionParams)
    {
        var sqlBuilder = new SqlConnectionStringBuilder
            {
                DataSource = buildConnectionParams.ServerName,
                InitialCatalog = buildConnectionParams.DatabaseName,
                IntegratedSecurity = true
            };

        var providerString = sqlBuilder.ToString();
        var entityBuilder = new EntityConnectionStringBuilder
        {
            Provider = buildConnectionParams.ProviderName,
            ProviderConnectionString = providerString,
            Metadata = string.Format(@"res://*/{0}.csdl|
                        res://*/{0}.ssdl|
                        res://*/{0}.msl", buildConnectionParams.ModelName)
        };

        return CreateConnection(buildConnectionParams.SchemaName, entityBuilder, buildConnectionParams.ModelName);
    }


    /// <summary>
    /// Creates the EntityConnection, based on new schema & existing connectionString
    /// </summary>
    /// <param name="schemaName">Name of the schema.</param>
    /// <param name="connectionBuilder"></param>
    /// <param name="modelName">Name of the model.</param>
    /// <returns></returns>
    private static EntityConnection CreateConnection(string schemaName, EntityConnectionStringBuilder connectionBuilder, string modelName)
    {
        Func<string, Stream> generateStream =
            extension => Assembly.GetExecutingAssembly().GetManifestResourceStream(string.Concat(modelName, extension));

        Action<IEnumerable<Stream>> disposeCollection = streams =>
        {
            if (streams == null)
                return;

            foreach (var stream in streams.Where(stream => stream != null))
                stream.Dispose();
        };

        var conceptualReader = generateStream(".csdl");
        var mappingReader = generateStream(".msl");
        var storageReader = generateStream(".ssdl");

        if (conceptualReader == null || mappingReader == null || storageReader == null)
        {
            disposeCollection(new[] { conceptualReader, mappingReader, storageReader });
            return null;
        }

        var storageXml = XElement.Load(storageReader);

        foreach (var entitySet in storageXml.Descendants())
        {
            var schemaAttribute = entitySet.Attributes("Schema").FirstOrDefault();
            if (schemaAttribute != null)
                schemaAttribute.SetValue(schemaName);
        }

        storageXml.CreateReader();

        var workspace = new MetadataWorkspace();

        var storageCollection = new StoreItemCollection(new[] { storageXml.CreateReader() });
        var conceptualCollection = new EdmItemCollection(new[] { XmlReader.Create(conceptualReader) });
        var mappingCollection = new StorageMappingItemCollection(conceptualCollection, 
                                                                storageCollection,
                                                                new[] { XmlReader.Create(mappingReader) });

        workspace.RegisterItemCollection(conceptualCollection);
        workspace.RegisterItemCollection(storageCollection);
        workspace.RegisterItemCollection(mappingCollection);

        var connection = DbProviderFactories.GetFactory(connectionBuilder.Provider).CreateConnection();
        if (connection == null)
        {
            disposeCollection(new[] { conceptualReader, mappingReader, storageReader });
            return null;
        }

        connection.ConnectionString = connectionBuilder.ProviderConnectionString;
        return new EntityConnection(workspace, connection);
    }
}

Použití:

/// <summary>
/// Initializes a new instance of the <see cref="DynamicAQDContext"/> class.
/// </summary>
public DynamicAQDContext()
{
    var entityConnection = DatabaseUtils.BuildConnection(new BuildConnectionParams
    {
        ProviderName = "System.Data.SqlClient",
        ServerName = "localhost\\",
        DatabaseName = "",
        ModelName = "YOURMODEL",
        SchemaName = "SCHEMA"
    });

    if(entityConnection == null)
        throw new Exception("Can't create EntityConnection");

    _entities = new LINKEntities(entityConnection);
}

více informací naleznete zde:http:/ /bestplayah.com/entity-framework-dynamic-schema-changes-using-database-first-approach/