Q:

How to sort Strings in C#

I have to sort an array of strings. How can I do that, if:

They must be placed in order of string length.
If lengths are equal, the must be placed alphabetically.

Is there any simple to do that ?

A:

Here's the traditional way in C# ...
static void Main(string[] args)
{
    List<string> list = new List<string>();
    list.Add("1991728819928891");
    list.Add("0991728819928891");
    list.Add("3991728819928891");
    list.Add("2991728819928891");
    list.Add("Hello");
    list.Add("World");
    list.Add("StackOverflow");
    list.Sort(
        delegate (string a, string b) {
            int result = a.Length.CompareTo(b.Length);
            if (result == 0 )
                result = a.CompareTo(b);
            return result;
        }
    );

    Console.WriteLine(string.Join("\n", list.ToArray()));
}

Sample Output:
Hello
World
StackOverflow
0991728819928891
1991728819928891
2991728819928891
3991728819928891

