using Linq would be:
listOfCompany.Where(c=> c.id == 1).FirstOrDefault().Name = "Whatever Name";
UPDATE
This can be simplified to be…
listOfCompany.FirstOrDefault(c=> c.id == 1).Name = "Whatever Name";
UPDATE
For multiple items (condition is met by multiple items):
listOfCompany.Where(c=> c.id == 1).ToList().ForEach(cc => cc.Name = "Whatever Name");