Expressions Vs Statements

expvsstat.cs

public static string ToUppercaseExpression(this string currentString) =>
    new string(currentString.Select(c => (char)(c < 97 || c > 122 ? c : c - 32)).ToArray());

public static string ToUppercaseStatements(this string currentString)
{
    var returnValue = new StringBuilder();
    foreach(var c in currentString)
    {
        if(c < 97 || c > 122)
        {
            returnValue.Append(c);
        }
        else
        {
            returnValue.Append((char)(c - 32));
        }
    }
    return returnValue.ToString();
}