For example using Linq:
string[] filePaths1 = { "7.1", "7.1", "7.2", "7.2", "7.3", "7.4" };
var qry = from s in filePaths1
group s by s into grp
select new{
num = grp.Key,
count = grp.Count()
};
foreach(var o in qry)
{
Console.WriteLine("{0} -> {1}", o.num, o.count);
}