Get minimum and maximum value using linq

If you want Min and Max value for each ID in the list, then you have to group by ID and the get MAX and Min accordingly like:

var query = yourList.GroupBy(r=> r.ID)
                    .Select (grp => new 
                              {
                                ID = grp.Key, 
                                Min = grp.Min(t=> t.Col1), 
                                Max = grp.Max(t=> t.Col2)
                              });

Use Enumerable.Max method to calculate maximum like:

var max = yourList.Max(r=> r.Col1);

Use Enumerable.Min method to calculate minimum on a field like:

var min = yourList.Min(r=> r.Col2);