实体框架和多个模式

Question

我正在尝试设置我的dbContext,以便它可以在单个Oracle数据库中处理多个模式.我不想要一个单片dbContext文件,所以我想出了以下内容:

public class oraDbContext : DbContext
{
    static oraDbContext() {
        Database.SetInitializer<oraDbContext>(null);
    }

    public oraDbContext(string connName)
        : base("Name=" + connName) { }

    public _schema1 schema1 = _schema1.Instance;
    public _schema2 schema2 = _schema2.Instance;

    protected override void OnModelCreating(DbModelBuilder modelBuilder) {
        schema1.OnModelCreating(modelBuilder);
        schema2.OnModelCreating(modelBuilder);
    }
}

模式文件如下所示:

public sealed class _schema1
{
    private static readonly _schema1 instance = new _schema1();

    static _schema1() { }
    private _schema1() { }

    public static _schema1 Instance {
        get {
            return instance;
        }
    }

    public DbSet<someTable> someTable { get; set; }

    internal void OnModelCreating(DbModelBuilder modelBuilder) {
        modelBuilder.Configurations.Add(new someTableMap());
    }
}

但是,当我尝试执行查询时,我收到错误:Value cannot be null.它引用的值是someTable_schema1中的属性.

A.我该如何解决这个问题？

B.有更好的解决方案吗？

编辑:我想要的是能够编写如下代码 -

var query1 = from p in db.schema1.someTable
             select p;
var query2 = from p in db.schema2.someTable
             select p;

其中someTable在两个模式中都是相同的.在我们的数据库中,我们有几个模式具有完全相同的表,这些表具有相同或几乎相同的列.我不想为每个模式创建一个单独的dbContext,因为如果我创建一个从5个模式中提取的查询,这可能意味着5个不同的连接.如果我在直接SQL中编写相同的查询,我可以通过单个连接从5个不同的模式中提取数据,这就是我想在这里完成的.

Answer 1

在对Entity Framework进行一些研究时,我遇到了以下帖子:

http://romiller.com/2011/05/23/ef-4-1-multi-tenant-with-code-first/

它并没有给我一个单独的dbContext,但它只使用一个连接(这是我不想使用多个dbContexts的原因).设置以下代码后:

public class oraDbContext : DbContext
{
    static oraDbContext() {
        Database.SetInitializer<oraDbContext>(null);
    }

    private oraDbContext(DbConnection connection, DbCompiledModel model)
        : base(connection, model, contextOwnsConnection: false) { }

    public DbSet<SomeTable1> SomeTable1 { get; set; }
    public DbSet<SomeTable2> SomeTable2 { get; set; }

    private static ConcurrentDictionary<Tuple<string, string>, DbCompiledModel> modelCache = new ConcurrentDictionary<Tuple<string, string>, DbCompiledModel>();

    public static oraDbContext Create(string schemaName, DbConnection connection) {
        var compiledModel = modelCache.GetOrAdd(
            Tuple.Create(connection.ConnectionString, schemaName),
            t =>
            {
                var builder = new DbModelBuilder();
                builder.Configurations.Add<SomeTable1>(new SomeTable1Map(schemaName));
                builder.Configurations.Add<SomeTable2>(new SomeTable2Map(schemaName));

                var model = builder.Build(connection);
                return model.Compile();
            });

        return new oraDbContext(connection, compiledModel);
    }
}

这当然要求我的映射文件设置如下:

public class DailyDependencyTableMap : EntityTypeConfiguration<DailyDependencyTable>
{
    public SomeTableMap(string schemaName) {
        this.ToTable("SOME_TABLE_1", schemaName.ToUpper());

        //Map other properties and stuff
    }
}

编写使用多个模式的查询有点令人讨厌,但目前,它完成了我需要它做的事情:

using (var connection = new OracleConnection("a connection string")) {
    using (var schema1 = oraDbContext.Create("SCHEMA1", connection))
    using (var schema2 = oraDbContext.Create("SCHEMA2", connection)) {

        var query = ((from a in schema1.SomeTable1 select new { a.Field1 }).ToList())
             .Concat((from b in schema2.SomeTable1 select new { b.Field1 }).ToList())
    }
}

 

Answer 2

您可以通过Table属性为每个表指定架构。

[Table(nameof(MyTable1), Schema = "Schema1")]
public class MyTable1 { }

[Table(nameof(MyTable2), Schema = "Schema2")]
public class MyTable2 { }