数组超出范围？该怎么处理

数组超出范围？

C# code

                int[] Iday =null;                for (int a = 0; a <= ehour; a++)                {                    Iday[a] = shour;                    shour++;                }

C# code

                int[] Iday = new int[ehour+1];                for (int a = 0; a <= ehour; a++)                {                    Iday[a] = shour;                    shour++;                }
[解决办法]
C# code
        int[] Iday = null;        for (int a = 0; a < Iday.Length; a++)        {            Iday[a] = shour;            shour++;        }