Question

What is the most efficient way to generate 10-character random alphanumeric string in c#?

Answer 1

Guid is pretty fast

Guid.NewGuid().ToString("N").Substring(0, 10);

From MSDN

A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated.

It might not be unique for a billion requests since you need only 10 characters. But it generates a string from 0 to 9 and A to F.

---

Performance

Tested using

public static void Test(Action a)
{
    Stopwatch sw = new Stopwatch();
    sw.Start();

    for (var i = 0; i < 10000; ++i)
        a();

    sw.Stop();

    Console.WriteLine("ms: {0} ticks: {1}", sw.ElapsedMilliseconds, sw.ElapsedTicks);
}

Guid method

Test(() =>
{
    var xxx = Guid.NewGuid().ToString("N").Substring(0, 10);
});

// Result
// 6     ms
// 17273 ticks

Bytes method

Test(() =>
{
    var buffer = new byte[5];
    new Random().NextBytes(buffer);
    var x = string.Join("", buffer.Select(b => b.ToString("X2")));
});

// Result:
// 57     ms
// 165642 ticks

It is up to you to pick between high speed or high reliability.