equals (C# Reference)
The equals contextual keyword is used in a join clause in a query expression to compare the elements of two sequences. For more information, see join clause (C# Reference).
Example
The following example shows the use of the equals keyword in a join clause.
var innerJoinQuery =
from category in categories
join prod in products on category.ID equals prod.CategoryID
select new { ProductName = prod.Name, Category = category.Name };