Strings in C# already have a char indexer
string test = "this is a test";
Console.WriteLine(test[0]);
And...
if(test[0] == 't')
Console.WriteLine("The first letter is 't'");
This works too...
Console.WriteLine("this is a test"[0]);
And this...
foreach (char c in "this is a test")
Console.WriteLine(c);
EDIT:
I noticed the question was updated with regards to char[] arrays. If you must have a string[] array, here's how you split a string at each character in c#:
string[] test = Regex.Split("this is a test", string.Empty);
foreach (string s in test)
{
Console.WriteLine(s);
}