在运行时更改数据库模式名称

Question

目前，在我的实体中，我有以下表定义：

[Table("SchemaName.SomeTable")]

我需要能够在运行时更改此模式名称。 我尝试分配一个变量，但它会引发错误。

作为第二次尝试，我删除了Table声明，而是在我的上下文的OnModelCreating中尝试使用以下内容进行设置：

modelBuilder.Entity<MY_VIEW>().ToTable("MYSCHEMA.MYVIEW");

这可行，但是，我现在希望能够在运行时通过我的 controller 更改它，因为 OnModelCreating 只触发一次。

Answer 1

为了使OnModelCreating为不同的模式运行，您需要覆盖IModelCacheKeyFactory的默认行为

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<ApplicationDbContext>(options =>
        {
            options.ReplaceService<IModelCacheKeyFactory, SchemaModelCacheKeyFactory>();
        });
    }
}

public class DatabaseOptions
{
    public string Schema { get; set; }
}

public class ApplicationDbContext : DbContext
{
    public string Schema { get; }

    public ApplicationDbContext(DbContextOptions options, IOptions<DatabaseOptions> databaseOptions)
        : base(options)
    {
        Schema = databaseOptions.Value.Schema;
    }


    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<MY_VIEW>().ToTable($"{Schema}.MYVIEW");
    }
}

public class SchemaModelCacheKeyFactory : ModelCacheKeyFactory
{
    public SchemaModelCacheKeyFactory(ModelCacheKeyFactoryDependencies dependencies)
        : base(dependencies)
    {
    }

    public override object Create(DbContext context)
    {
        if (context is ApplicationDbContext applicationDbContext)
        {
            return new SchemaModelCacheKey(context, applicationDbContext.Schema);
        }
        else
        {
            return base.Create(context);
        }
    }
}

public class SchemaModelCacheKey : ModelCacheKey
{
    public SchemaModelCacheKey(DbContext context, string schema) : base(context)
    {
        _schema = schema;
    }

    private readonly string _schema;

    protected virtual bool Equals(SchemaModelCacheKey other) => _schema == other._schema && base.Equals(other);

    public override bool Equals(object obj) => (obj is SchemaModelCacheKey otherAsKey) && Equals(otherAsKey);

    public override int GetHashCode() => base.GetHashCode() + _schema.GetHashCode();
}