[c#] Split string and get first value only

These are the two options I managed to build, not having the luxury of working with var type, nor with additional variables on the line:

string f = "aS.".Substring(0, "aS.".IndexOf("S"));
Console.WriteLine(f);

string s = "aS.".Split("S".ToCharArray(),StringSplitOptions.RemoveEmptyEntries)[0];
Console.WriteLine(s);

This is what it gets:

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