The System.Linq namespace provides classes and interfaces that support queries that use Language-Integrated Query (LINQ).
The Enumerable class contains LINQ standard query operators that operate on objects that implement IEnumerable<(Of <(T>)>).
The Queryable class contains LINQ standard query operators that operate on objects that implement IQueryable<(Of <(T>)>).
Why does the compiler say that 'Linq' does not exist in the 'System' namespace when specifying a using statement as follows:
using System.Linq;
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Answer :
Add System.Core reference ( version 3.5 )