System.ComponentModel.MaskedTextProvider.TestString C# (CSharp) Method

        private bool TestString(string input, int position, out int testPosition, out MaskedTextResultHint resultHint)
        {
            Debug.Assert(input != null, "null input.");
            Debug.Assert(position >= 0, "Position out of range.");

            resultHint = MaskedTextResultHint.Unknown;
            testPosition = position;

            if (input.Length == 0)
            {
                return true;
            }

            // If any char is actually accepted, then the hint is success, otherwise whatever the last character result is.
            // Need a temp variable for 
            MaskedTextResultHint tempHint = resultHint;

            foreach (char ch in input)
            {
                if (testPosition >= _testString.Length)
                {
                    resultHint = MaskedTextResultHint.UnavailableEditPosition;
                    return false;
                }

                // If character is not to be escaped, we need to find an edit position to test it in.
                if (!TestEscapeChar(ch, testPosition))
                {
                    testPosition = FindEditPositionFrom(testPosition, forward);

                    if (testPosition == invalidIndex)
                    {
                        testPosition = _testString.Length;
                        resultHint = MaskedTextResultHint.UnavailableEditPosition;
                        return false;
                    }
                }

                // Test/Set char will scape prompt, space and literals if needed.
                if (!TestChar(ch, testPosition, out tempHint))
                {
                    resultHint = tempHint;
                    return false;
                }

                // Result precedence: Success, SideEffect, NoEffect, CharacterEscaped.
                if (tempHint > resultHint)
                {
                    resultHint = tempHint;
                }

                testPosition++;
            }

            testPosition--;

            return true;
        }