How can I find out if a strongly typed table contains a value from another strongly typed table in C# using Linq

Question

I have two strongly tabled tables for Customers with Locations, which have the columns "CustomerCode" and "Location".

In Customer A, there are the following rows:

"A", 1
"A", 2
"A", 3

In Customer B, there are the following rows:

"B", 2
"B", 5
"B", 6

How can I use Linq to workout whether Customer B has any Locations, the same as Customer A.

I want to do something like this foreach but in linq:

var doesExist = false; 
foreach(var a in customersA)
{
   if (customersB.Select(b => b.Location).Contains(a.Location))
   {
      doesExist = true;
      break;
   }
 }

For example, I want to do something like this:

customersA.Select(a => a.Location).Any(customersB.Select(b => b.Location)

Answer 1

Note I'm assuming you want one bool that determines whether or not there is any customer in both tables that share a Location. AND assuming you don't care which customer(s) had the match - just that there was a match at all.

If you want it all in LINQ statements, nest the Any statements, then compare the Location property:

bool sameLocationFound = customersB.Any(b => customersA.Any(a => a.Location == b.Location));

I read this code as "find whether any customer B exists such that any customer A shares a location with B".

Answer 2

You can use Intersect like below

var location_in_CustA = customersA.Select(a => a.Location);
var location_in_CustB = customersB.Select(b => b.Location);

var intersectionRecords = location_in_CustA.Intersect(location_in_CustB);
var exists = intersectionRecords.Count() > 1;

Produces the set intersection of two sequences.

Answer 3

Another way is using let keyword:

var query = (from c in customerA
             let locations = customerB.Select(c => c.Location)
             where locations.Any(l => l == c.Location)
            ).ToList();