Array Initialization and actual number of elements in the ar

Question

Do we need to initialize array?

I have a following piece of code

string[] monthToProcess=new string[12];

            int i = 0;
            foreach (DataColumn column in ds.Tables[0].Columns)
            {
               
                if (column.ColumnName.Contains(monthColumnString))
                {  
                  
                    monthToProcess[i] = column.ColumnName;

                    i = i + 1;
               
                }
            }
           int j = monthToProcess.Length;

If I don't initialize array

instead of string[] monthToProcess=new string[12];

if I have only string[] monthToProcess;

I get error

But if initialize to its maximum size which is 12 then no matter if I have 2 elements I get monthToProcess.Length

I want it should give me the length as 2 (actual number of elements in the array).

How to do this?