Question

I’ve got a problem and no idea how to solve it. Imagine you have a List<int> with about 6000 unique id’s that matches the id’s of a table with about a million records in a sql datatable. I want to select those 6000 records that matches those id’s via LINQ from my c# program. I don’t want to use Contains() because it gets very slow in translation and the argumentlist gets to big.

Any other ideas how to solve this ?

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Something about my scenario ( this is not the real but a similar scenario ) :

I’ve got a Service that is connected to a database. A Client requests a batch of Items like a Person for example. The Service accepts the requests, query the DB and sends the data back to the client.

Person = (PersonID , Prename, Lastname)

Now the Client holds a temporary List of Persons. With an additional method I would like to retrieve the adresses of these Persons from the service. So I put a List of PersonID’s to the service that should give me back a list of Adresses that have references to those persons.

Answer 1

If you are using Entity Framework (EF) you can use inner join between your data (data) and your table (Customers)

void Main()
{    
    var data = Enumerable.Range(1, 6000);

    var result = from x in data
    join y in Customers
    on x equals y.CustomerID
    select x;

    result.Dump();
}