Find the first character in a string that is a letter

There are several ways to do this. Two examples:

string s = "12345Alpha";
s = new string(s.TakeWhile(Char.IsDigit).ToArray());

Or, more correctly, as Baldrick pointed out in his comment, find the first letter:

s = new string(s.TakeWhile(c => !Char.IsLetter(c)).ToArray());

Or, you can write a loop:

int pos = 0;
while (!Char.IsLetter(s[pos]))
{
    ++pos;
}
s = s.Substring(0, pos);

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