Leetcode Roman to arabic number

public int RomanToInt(string s)
    {
        int number = 0;
        char prevChar = 'a';
        int prevAdded = 0;
        foreach (char item in s)
        {
            if (item == 'I')
            {
                prevChar = 'I';
                prevAdded = 1;
                number += 1;
            }
            else if(item == 'V')
            {
                if (prevChar == 'I')
                {
                    number -= prevAdded;
                    prevAdded = 0;
                    number += 4;
                    prevChar = 'V';
                }
                else
                {
                    prevAdded = 5;
                    prevChar = 'V';
                    number += 5;
                }
            }
            else if(item == 'X')
            {
                if (prevChar == 'I')
                {
                    number -= prevAdded;
                    prevAdded = 0;
                    number += 9;
                    prevChar = 'X';
                }
                else
                {
                    prevAdded = 10;
                    prevChar = 'X';
                    number += 10;
                }
            }
            else if(item == 'L')
            {
                if (prevChar == 'X')
                {
                    number -= prevAdded;
                    prevAdded = 0;
                    number += 40;
                    prevChar = 'L';
                }
                else
                {
                    prevAdded = 50;
                    prevChar = 'L';
                    number += 50;
                }
            }
            else if(item == 'C')
            {
                if (prevChar == 'X')
                {
                    number -= prevAdded;
                    prevAdded = 0;
                    number += 90;
                    prevChar = 'C';
                }
                else
                {
                    prevAdded = 100;
                    prevChar = 'C';
                    number += 100;
                }
            }
            else if(item == 'D')
            {
                if (prevChar == 'C')
                {
                    number -= prevAdded;
                    prevAdded = 0;
                    number += 400;
                    prevChar = 'D';
                }
                else
                {
                    prevAdded = 500;
                    prevChar = 'D';
                    number += 500;
                }
            }
            else if(item == 'M')
            {
                if (prevChar == 'C')
                {
                    number -= prevAdded;
                    prevAdded = 0;
                    number += 900;
                    prevChar = 'M';
                }
                else
                {
                    prevAdded = 1000;
                    prevChar = 'M';
                    number += 1000;
                }
            }
        }
        return number;
    }