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There are many different ways to handle multi-tenancy. This blog post will cover one approach to EF Core Multi-Tenancy that will work if you are using a shared database approach, meaning you use the same database for multiple tenants, that are disambiguated using tenant ID column.
If you want more details on Multi-Tenancy, check out the Microsoft Docs on the topic, related to designing multi-tenant apps using Azure SQL Database.
Entity
Let’s jump right into some sample code of a simple Entity that represents a customer. Notice theTenantId.
Filter
The approach we are going to use is to pre-filter anyDbSet in our DbContext. We can do this by using the EntityFramework-Plus package.
It provides us the ability to specify per context instance how to pre-filter our DbSets. We can do this by adding our TenantId as a ctor parameter and use the Filter<T> extension method.
Example Usage
Here’s a small console app that adds two new customer records both with the sameCustomerId = 1. When creating the MyDbContext, we the TenantId we want to pre-filter on.
That’s cool, but does the filter only apply when you query the entity by itself, or does filter take into account when that resource is used in a projected query?
To be clear so I can actually create an sample, can you give me an example?
“`
var summary =
(from customer in db.Customers
select new {
customerName = customer.Name,
numberOfOrders = customer.Orders.Count()
})
.ToList()
“`
Is the filter applied when I call `db.Customers` in the LINQ query? I would assume so. Also, what about?
“`
var summary =
(from order in db.Orders
select new {
customerName = order.Customer.Name,
total = order.Total,
tax = order.Tax
})
.ToList()
“`
Correct, it’s applied when calling the db.Customers or db.Orders, whichever you have the filter specified for.
SQL produced is:
SELECT [o].[OrderId], [o.Customer].[Name] AS [customerName]
FROM [Orders] AS [o]
LEFT JOIN [Customers] AS [o.Customer] ON [o].[CustomerId] = [o.Customer].[CustomerId]
WHERE [o].[TenantId] = @__TenantId_0
Had forgotten about the EF Plus package. Thanks for that! Lots of good stuff there.
In this scenario – any benefit of using that package over EF Core 2’s HasQueryFilter option?
Wow! I never even knew this existed. Thanks for letting me know. I was just checking it out and it looks like this is equivalent to EF Plus package. Basically add the tenant filter in the OnModelCreating.
How does this dffer from using EFCore’s modelBuilder:
builder.Entity(entity =>
{
entity.HasQueryFilter(x => x.Where(q => q.TenantId == TenantId));
});
Worth mentioning when having instance values on the context to be careful when considering using db context pooling.