实体框架核心中的动态变化模式 [英] Dynamically changing schema in Entity Framework Core
问题描述
解决方法，在必要时提供数据库上下文 public static void Resolve（IServiceCollection services）{
services.AddIdentity< ApplicationUser，IdentityRole>（）
.AddEntityFrameworkStores< DomainDbContext>（）
.AddDefaultTokenProviders（）;
services.AddTransient< IOrderProvider，OrderProvider>（）;
...
}
我可以在 OnModelCreating ，但是，如之前发现的，此方法只调用一次，因此我可以在这里设置模式名globaly，如下
protected override void OnModelCreating（ModelBuilder modelBuilder）{
modelBuilder.HasDefaultSchema（public）;
base.OnModelCreating（modelBuilder）;
}
或在模型中通过类似的
[Table（order，Schema =public）]
public class Order {...}
但是如何在运行时更改模式名称？我每个请求创建ef的上下文，但是首先，我通过请求向用户发送模式名称到数据库中的一些模式共享表。那么组织这个机制的真正方法是什么？
- 根据用户的凭据计算出模式名称;
谢谢。
PS我使用PostgreSql，这是表格名称较低的原因。
您是否已经在EF6中使用EntityTypeConfiguration？
我认为解决方案将在DbContext类中使用OnModelCreating方法上的实体映射，如下所示：
使用系统;
使用Microsoft.EntityFrameworkCore;
使用Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
使用Microsoft.Extensions.Options;
命名空间AdventureWorksAPI.Models
{
public class AdventureWorksDbContext：Microsoft.EntityFrameworkCore.DbContext
{
public AdventureWorksDbContext（IOptions< AppSettings> appSettings）
{
ConnectionString = appSettings.Value.ConnectionString;
}
public String ConnectionString {get;
protected override void OnConfiguring（DbContextOptionsBuilder optionsBuilder）
{
optionsBuilder.UseSqlServer（ConnectionString）;
//此块强制映射方法调用每个实例
var builder = new ModelBuilder（new CoreConventionSetBuilder（）。CreateConventionSet（））;
OnModelCreating（builder）;
optionsBuilder.UseModel（builder.Model）;
}
protected override void OnModelCreating（ModelBuilder modelBuilder）
{
modelBuilder.MapProduct（）;
base.OnModelCreating（modelBuilder）;
}
}
}
OnConfiguring方法的代码强制在DbContext类的每个实例创建上执行MapProduct。
MapProduct方法的定义：
使用系统;
使用Microsoft.EntityFrameworkCore;
命名空间AdventureWorksAPI.Models
{
public static class ProductMap
{
public static ModelBuilder MapProduct（此ModelBuilder modelBuilder，String模式）
{
var entity = modelBuilder.Entity< Product>（）;
entity.ToTable（Product，schema）;
entity.HasKey（p => new {p.ProductID}）;
entity.Property（p => p.ProductID）.UseSqlServerIdentityColumn（）;
return modelBuilder;
}
}
}
如上图所示，有一行为表格设置模式和名称，您可以在DbContext中为一个构造函数发送模式名称或类似的东西。
请不要使用魔术字符串，您可以使用所有可用的模式创建一个类，例如：
using System;
public class Schemas
{
public const String HumanResources =HumanResources;
public const String Production =Production;
public const String Sales =Production;
}
要创建具有特定架构的DbContext，可以这样写：
var humanResourcesDbContext = new AdventureWorksDbContext（Schemas.HumanResources）;
var productionDbContext = new AdventureWorksDbContext（Schemas.Production）;
显然，您应该根据模式名称参数的值设置模式名称：
entity.ToTable（Product，schemaName）;
I have an issue with working with EF Core. I want to separate data for different companies in my project's database via schema-mechanism. My question is how I can change schema name in runtime? I've found similar question about this issue but it's still ananswered and I have some different conditions. So I have Resolve method that grants db-context when necessary
public static void Resolve(IServiceCollection services) {
services.AddIdentity<ApplicationUser, IdentityRole>()
.AddEntityFrameworkStores<DomainDbContext>()
.AddDefaultTokenProviders();
services.AddTransient<IOrderProvider, OrderProvider>();
...
}
I can set schema-name in OnModelCreating, but, as was found before, this method called just once, so I can set schema name globaly here like that
protected override void OnModelCreating(ModelBuilder modelBuilder) {
modelBuilder.HasDefaultSchema("public");
base.OnModelCreating(modelBuilder);
}
or right in model via attribute like that
[Table("order", Schema = "public")]
public class Order{...}
But how can I change schema name in runtime? I create ef's context per each request, but firstly I fugure out schema-name for user via request to some schema-shared table in database. So what is the true-way to organize that mechanism:
- Figure out schema name by user's credentials;
- Get user-specific data from database from specific schema.
Thank you.
P.S. I use PostgreSql and this is a reason of lowecased table name.
Did you already use EntityTypeConfiguration in EF6?
I think the solution would be use mapping for entities on OnModelCreating method in DbContext class, something like this:
using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
using Microsoft.Extensions.Options;
namespace AdventureWorksAPI.Models
{
public class AdventureWorksDbContext : Microsoft.EntityFrameworkCore.DbContext
{
public AdventureWorksDbContext(IOptions<AppSettings> appSettings)
{
ConnectionString = appSettings.Value.ConnectionString;
}
public String ConnectionString { get; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(ConnectionString);
// this block forces map method invoke for each instance
var builder = new ModelBuilder(new CoreConventionSetBuilder().CreateConventionSet());
OnModelCreating(builder);
optionsBuilder.UseModel(builder.Model);
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.MapProduct();
base.OnModelCreating(modelBuilder);
}
}
}
The code on OnConfiguring method forces the execution of MapProduct on each instance creation for DbContext class.
Definition of MapProduct method:
using System;
using Microsoft.EntityFrameworkCore;
namespace AdventureWorksAPI.Models
{
public static class ProductMap
{
public static ModelBuilder MapProduct(this ModelBuilder modelBuilder, String schema)
{
var entity = modelBuilder.Entity<Product>();
entity.ToTable("Product", schema);
entity.HasKey(p => new { p.ProductID });
entity.Property(p => p.ProductID).UseSqlServerIdentityColumn();
return modelBuilder;
}
}
}
As you can see above, there is a line to set schema and name for table, you can send schema name for one constructor in DbContext or something like that.
Please don't use magic strings, you can create a class with all available schemas, for example:
using System;
public class Schemas
{
public const String HumanResources = "HumanResources";
public const String Production = "Production";
public const String Sales = "Production";
}
For create your DbContext with specific schema you can write this:
var humanResourcesDbContext = new AdventureWorksDbContext(Schemas.HumanResources);
var productionDbContext = new AdventureWorksDbContext(Schemas.Production);
Obviously you should to set schema name according schema's name parameter's value:
entity.ToTable("Product", schemaName);
这篇关于实体框架核心中的动态变化模式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
