How to calculate sum of a DataTable’s Column in LINQ (to Dataset)?

If untyped (replace int with the correct data type):

 var sum = table.AsEnumerable().Sum(x=>x.Field<int>(3));

or:

 var sum = table.AsEnumerable().Sum(x=>x.Field<int>("SomeProperty"));

If typed:

 var sum = table.Sum(x=>x.SomeProperty);