Get sum of the value from list using linq?

Question

I am trying to get the sum of the value from list of list using linq ?my data is as below code

        List> allData = new List<         


        

Answer 1

var grouped = allData.GroupBy(x => x[0])
                     .Select(g => new
                     {
                         Name = g.Key,
                         Sum = g.Sum(x => int.Parse(x[2]))
                     });

It will return an anonymous type instance for each group, with two properties: Name with your grouping key and Sum with sum of marks.