如何以编程方式选择 DbConfigurationType?

How to choose DbConfigurationType programmatically?(如何以编程方式选择 DbConfigurationType?)

问题描述

我有一个DbContext:

[DbConfigurationType(typeof(MySqlEFConfiguration))]
public class MyDbContext : DbContext
{
    public DbSet<MyClass> MyClasses { get; set; }
}

现在，如果我希望能够根据 AppSettings 值使用另一个 DbConfigurationType 怎么办?

Now, what if I want to be able to use another DbConfigurationType, according to AppSettings value?

因此，我将 AppSettings 的值从 MySQL 更改为 MSSQL，它变为:

So that, I change AppSettings value from MySQL to MSSQL and it becomes:

[DbConfigurationType(typeof(MsSqlEFConfiguration))]
public class MyDbContext : DbContext
{
    public DbSet<MyClass> MyClasses { get; set; }
}

当然，我可以创建一个工厂，并使用反射创建一个具有自定义属性的新类.但是，有没有不反思的解决方案?

Of course, I can create a factory, and use reflection to create a new class with custom attribute. However, is there a solution without reflection?

推荐答案

我已经通过继承DbConfigurationTypeAttribute解决了这个问题:

I have solved the problem by inheriting from DbConfigurationTypeAttribute:

public class BaseEfConfiguration : DbConfigurationTypeAttribute
{
    public BaseEfConfiguration() : base(SqlConfiguration)
    {
    }

    public static Type SqlConfiguration
    {
        get
        {
            string databaseTypeName = ConfigurationManager.AppSettings["DatabaseType"];
            switch (databaseTypeName)
            {
                case "MySQL":
                    return typeof(MySqlEFConfiguration);
                case "MSSQL":
                    return typeof(MsSqlEFConfiguration);
                default:
                    throw new NotImplementedException($"No such SQL configuration type {databaseTypeName}");
            }
        }
    }
}

[BaseEfConfiguration]
public class BaseDbContext : DbContext
{

}

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