Autofac parameter resolving from Model into Repository - autofac

Question

How can I set parameter from Model: DatabaseName into MyRepository constructor during Autofac container registration?
Here is code sample:
public class ModelBase
{
public string DatabaseName;
}
public interface IRepository<TEntity>
where TEntity : ModelBase
{
}
public class MyRepository<TEntity> : IRepository<TEntity>
where TEntity : ModelBase
{
private readonly string _connectionString;
public MyRepository(string databaseName)
{
_connectionString = string.Format("DatabaseName='{0}';...", databaseName);
}
}
class Program
{
static void Main(string[] args)
{
var containerBuilder = new ContainerBuilder();
containerBuilder.RegisterGeneric(typeof(MyRepository<>)).As(typeof(IRepository<>));
IContainer container = containerBuilder.Build();
var someRepository = container.Resolve<IRepository<ModelBase>>();
}
}

Answer 1

As far as I understand, you can try to extract value of DatabaseName from the generic argument of the repository using kinda code:
public class ModelBase
{
public virtual string DatabaseName { get; } = "MyDataBase";
}
public class SubModelBase : ModelBase
{
public override string DatabaseName { get; } = "AnotherDataBase";
}
public interface IRepository<TEntity>
where TEntity : ModelBase
{
}
public class MyRepository<TEntity> : IRepository<TEntity>
where TEntity : ModelBase
{
private readonly string _connectionString;
public MyRepository(string databaseName)
{
_connectionString = string.Format("DatabaseName='{0}';...", databaseName);
}
}
class Program
{
static void Main(string[] args)
{
var containerBuilder = new ContainerBuilder();
containerBuilder.RegisterGeneric(typeof(MyRepository<>)).As(typeof(IRepository<>)).WithParameter((p, ctx) => true, (p, ctx) =>
{
var repType = p.Member.DeclaringType;
var genericParamType = repType.GenericTypeArguments[0];
var prop = genericParamType.GetProperty("DatabaseName");
var databaseName = prop.GetValue(Activator.CreateInstance(genericParamType));
// or for static DatabaseName
// var databaseName = prop.GetValue(null);
return databaseName;
});
IContainer container = containerBuilder.Build();
var someRepository = container.Resolve<IRepository<ModelBase>>();
var anotherRepository = container.Resolve<IRepository<SubModelBase>>();
}
}
Notice that DatabaseName must be determined for default ModelBase instance and type must have parameterless constructor. Or you can make DatabaseName static and make it assign it at compile time. In this case you can call var databaseName = prop.GetValue(null);.