Create DbContext dynamically for multiple database architecture with repect to logged-in user

Question

I am working on multi layered architecture with supporting multiple database per tenant in MVC. I need to create DBContext depending on the user logged in into data layer. How should I create generic DBContext and set connection string according to user?

Following is code to get connection string from Host Databsae and set it to Client Database. (In data/repository layer)

private static string GetConnectionString()
{
    int tenantId;
    HostDBContext hostContext = new HostDBContext();

    //Get Tenant and set ID to get required connection string
    tenantId = 1; //Get Tenant Id from session

    var tenantDetails = hostContext.TenantDetails.Find(tenantId);

    if (tenantDetails != null)
    {
        return tenantDetails.connectionstring;
    }

    return "default connection string";
}

Answer 1

You're on the right track, but it won't be a generic DbContext , just one that with a connection string that's set at runtime. So instead of GetConnectionString, you want to create a DbContext factory that requires the tenant Id to return your new DbContext("connectionString").

Let's call it TenantDbContext :

public class TenantDbContext : DbContext
{
    public TenantDbContext(string connectionString) : base(connectionString)
    {
    }
// Or
    public TenantDbContext(int tenantId) : base(GetConnectionString(tenantId))
    {
    }
}

if using a factory:

public class TenantDbContextFactory : IDbContextFactory<TenantDbContext, int>
{
    public TenantDbContext Create(int tenantId)
    {
        var connectionString = GetConnectionString(tenantId);
        return new TenantDbContext(connectionString);
    }
    // ... rest of factory
}

public interface IDbContextFactory<TContext, TKey> where TContext :DbContext
{
     TContext Create(TKey key);
}

If you're using a dependency injection container, you can also wire it up to return the TenantDbContext based on the tenant Id.