c＃code - System.NullReferenceException：未将对象引用设置为对象的实例

Question

如果将null传递给compare函数，则代码会抛出以下异常。

我如何处理null？

  

System.NullReferenceException：未将对象引用设置为对象的实例;

public static bool Compare(string s1, string s2)
{ 
    var array1 = s1.ToUpper().ToCharArray();
    var array2 = s2.ToUpper().ToCharArray();

    int count1 = array1.Count();
    int count2 = array2.Count();

    int verify1 = 0;
    int verify2 = 0;

    int sum1 = 0;
    int sum2 = 0;

    for (int i = 0; i < count1; i++)
    {
        verify1 = (int)array1[i];
        sum1 += (int)array1[i];

            if (verify1 < 65 || verify1 > 90)
            {
                sum1 = 0;
                count1 = i;                         
            }
    }

    for (int j = 0; j < count2; j++)
    {
        verify2 = (int)array2[j];
        sum2 += (int)array2[j];

        if (verify2 < 65 || verify2 > 90)
        {
            sum2 = 0;
            count2 = j;
        }
    }

    if (sum1 == sum2)
    {
        return true;
    }
    else
    {
        return false;
    }

}