Initializing an integer array

string dosage = "2/3/5 mg";
string[] dosageStringArray = dosage.Split('/');
int[] dosageIntArray = null;
for (int i = 0; i <= dosageStringArray.Length; i++) 
{
    if (i == dosageStringArray.Length)
    {
        string[] lastDigit = dosageStringArray[i].Split(' ');
        dosageIntArray[i] = Common.Utility.ConvertToInt(lastDigit[0]);
    }
    else
    {
        dosageIntArray[i] = Common.Utility.ConvertToInt(dosa开发者_JAVA技巧geStringArray[i]);
    }
}

I am getting the exception on this line: dosageIntArray[i] = Common.Utility.ConvertToInt(dosageStringArray[i]); I am unable to resolve this issue. Not getting where the problem is. But this line int[] dosageIntArray = null; is looking suspicious.

Exception: Object reference not set to an instance of an object.

The biggest problem with your solution is not the missing array declaration, but rather how you'd parse the following code:

string dosage = "2/13/5 mg";

Since your problem is surely domain specific, this may not arise, but some variation of two digits representing same integer.

The following solution splits the string on forward slash, then removes any non-digits from the substrings before converting them to integers.

Regex digitsOnly = new Regex(@"[^\d]");   
var array = dosage.Split('/')
                  .Select(num => int.Parse(digitsOnly.Replace(num, string.Empty)))
                  .ToArray();

Or whatever that looks like with the cuddly Linq synthax.

You are looking for something like

int[] dosageIntArray = new int[dosageStringArray.Length];

You are trying to access a null array (dosageIntArray) here:

dosageIntArray[i] = Common.Utility.ConvertToInt(lastDigit[0]);

You need to initialize it before you can access it like that.

You have to allocate dosageIntArray like this:

in[] dosageIntArray = new int[dosageStringArray.Length];

Also, you have another bug in your code: Index of last element of an array is Length - 1. Your for statement should read as:

for (int i = 0; i < dosageStringArray.Length; i++)

or

for (int i = 0; i <= (dosageStringArray.Length - 1); i++)

The former is preferred and is the most common style you will see.

I strongly recommend you use Lists instead of Arrays. You don't need to define the size of the List; just add items to it. It's very functional and much easier to use.

As alternative approach:

var dosage = "2/3/5 mg";
int[] dosageIntArray = Regex.Matches(dosage, @"\d+")
                            .Select(m => int.Parse(m.Value))
                            .ToArray();