System.Tests.StringTests.ToLowerToUpperInvariant_ASCII C# (CSharp) Method

        public static void ToLowerToUpperInvariant_ASCII()
        {
            var asciiChars = new char[128];
            var asciiCharsUpper = new char[128];
            var asciiCharsLower = new char[128];

            for (int i = 0; i < asciiChars.Length; i++)
            {
                char c = (char)i;
                asciiChars[i] = c;

                // Purposefully avoiding char.ToUpper/ToLower here so as not  to use the same thing we're testing.
                asciiCharsLower[i] = (c >= 'A' && c <= 'Z') ? (char)(c - 'A' + 'a') : c;
                asciiCharsUpper[i] = (c >= 'a' && c <= 'z') ? (char)(c - 'a' + 'A') : c;
            }

            var ascii = new string(asciiChars);
            var asciiLower = new string(asciiCharsLower);
            var asciiUpper = new string(asciiCharsUpper);

            Assert.Equal(asciiLower, ascii.ToLowerInvariant());
            Assert.Equal(asciiUpper, ascii.ToUpperInvariant());
        }