[Solved]-Group and Merge multiple values from single List using LINQ-LINQ,C#

for your outputtest list, you can get themax of dead_alive and blocked_unblocked after grouping, like the following code:

var groups = output.groupby(x => x.id_number)
    .select(y => new cls_entry
    {
        id_number = y.key,
        dead_alive = y.max(e => e.dead_alive),
        blocked_unblocked = y.max(e => e.blocked_unblocked)
    }).tolist();

documentation of max method : max