Roman to int C# Program

Program.cs

/*
    * C# Program to Convert Roman to Arabic Numerals
    
*/

static int RomanToInt(int decimalNumber, int i, string romanString)
{
    var romanChar = TryGetCharAt(romanString, i);
    return romanChar switch
    {
        'I' when TryGetCharAt(romanString, i + 1) == 'V' => RomanToInt(decimalNumber + 4, i + 2, romanString),
        'I' => RomanToInt(decimalNumber + 1, ++i, romanString),
        'V' => RomanToInt(decimalNumber + 5, ++i, romanString),
        'X' when TryGetCharAt(romanString, i + 1) == 'L' => RomanToInt(decimalNumber + 40, i + 2, romanString),
        'X' => RomanToInt(decimalNumber + 10, ++i, romanString),
        'L' => RomanToInt(decimalNumber + 50, ++i, romanString),
        'C' when TryGetCharAt(romanString, i + 1) == 'D' => RomanToInt(decimalNumber + 400, i + 2, romanString),
        'C' when TryGetCharAt(romanString, i + 1) == 'M' => RomanToInt(decimalNumber + 900, i + 2, romanString),
        'C' => RomanToInt(decimalNumber + 100, ++i, romanString),
        'D' => RomanToInt(decimalNumber + 500, ++i, romanString),
        'M' => RomanToInt(decimalNumber + 1000, ++i, romanString),
        _ => decimalNumber,
    };
}

static char TryGetCharAt(string romanString, int i)
{
    return i < romanString.Length ? romanString[i] : ' ';
}

var romanString = args[0].ToUpper();
var romanConverted = RomanToInt(0, 0, romanString);
Console.WriteLine($"Roman Number : {romanString} = {romanConverted}");