use Array.Sort() method
static void Main()
{
string[] a = new string[]
{
"delhi",
"mbd",
"bly",
"rmp",
"gzb",
};
Array.Sort(a);
foreach (string s in a)
{
Console.WriteLine(s);
}
or you can use sorting algorithm in C#
Bubble Sort in C#
Insertion sort
for more try Google