[英]Entity Framework and multiple schemas
I'm trying to set up my dbContext so that it can handle multiple schemas in a single Oracle database. 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。 I didn't want one monolithic dbContext file so I've come up with the following: 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);
}
}
The schema file looks like this: 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());
}
}
However, when I try to perform a query I get the error: Value cannot be null
. 但是,当我尝试执行查询时,我收到错误: Value cannot be null
。 The value it's referring to is the someTable
property in _schema1. 它引用的值是someTable
中的someTable
属性。
A. How can I fix this? A.我该如何解决这个问题?
B. Is there a better solution? B.有更好的解决方案吗?
Edit: What I want here is the ability to write code such as the following - 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;
Where someTable is the same in both schemas. 其中someTable在两个模式中都是相同的。 In our database we have several schemas with the exact same tables that have identical or nearly identical columns. 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。 I don't want to create a seperate dbContext for each schema because that could potentially mean 5 different connections if I'm creating a query that pulls from 5 schemas. 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。 If I was writing this same query in straight SQL I could pull the data from 5 different schemas with a single connection and that's what I would like to accomplish here. 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。
While doing some research about Entity Framework I came across the following post: 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/ http://romiller.com/2011/05/23/ef-4-1-multi-tenant-with-code-first/
It doesn't quite give me a single dbContext to work with but it does only use a single connection (which was my reasoning behind not wanting to use multiple dbContexts). 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)。 After setting up the following code: 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);
}
}
This of course requires that my mapping files be set up like so: 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
}
}
Writing queries that use multiple schemas is somewhat annoying but, for the moment, it does what I need it to do: 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())
}
}
Try using partial classes instead 请尝试使用部分类
public partial class oraDbContext : DbContext
{
static oraDbContext() {
Database.SetInitializer<oraDbContext>(null);
}
public oraDbContext(string connName)
: base("Name=" + connName) { }
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
schema1(modelBuilder);
schema2(modelBuilder);
}
}
public partial class oraDbContext : DbContext
{
public DbSet<someTable> someTable { get; set; }
void schema1(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new someTableMap());
}
}
You can specify schema per table via Table
attribute. 您可以通过Table
属性为每个表指定模式。
[Table(nameof(MyTable1), Schema = "Schema1")]
public class MyTable1 { }
[Table(nameof(MyTable2), Schema = "Schema2")]
public class MyTable2 { }
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