Freeing memory, static class destructor?

Question

I have a static class that I use as my data layer on my website. In this class, I have string arrays that store the requested data, which I can access later. Here is part of my class and the method in question:

public static class data_layer
{
    private static string[] items;
    private static string[] description;

    //will return description for an item id. if no item id is found, null is returned
    public static string getDesc(string key)
    {
        int i = 0;
        bool flag = false;
        //search for the item id to find its index
        for(i = 0; i < items.Length; i++)
        {
            if(items[i] == key)
            {
                flag = true;
                break;
            }
        }
        if(flag)
            return description[i];
        else
            return null;
    }
    public static string[] getItems()
    {
        return items;
    }

    public static bool setItemsAndDescriptions()
    {
        ArrayList itemIDs = new ArrayList();
        ArrayList itemDescs = new ArrayList();

        SqlConnection sqlConn = new SqlConnection();
        sqlConn.ConnectionString = ConfigurationManager.ConnectionStrings["MAS200RAWConnectionString"].ConnectionString;
        string query = "SELECT ItemNumber, ItemDescription FROM OUS_IM1_InventoryMasterfile " +
            "WHERE ItemNumber LIKE 'E%' OR ItemNumber LIKE 'B%' OR ItemNumber LIKE 'D%'";

        try
        {
            sqlConn.Open();
            SqlCommand sqlComm = new SqlCommand();
            sqlComm.Connection = sqlConn;
            sqlComm.CommandType = CommandType.Text;
            sqlComm.CommandText = query;
            SqlDataReader reader = sqlComm.ExecuteReader();
            if (reader == null)
                return false;

            //add the queried items to the ddl
            while (reader.Read())
            {
                itemIDs.Add(reader["ItemNumber"].ToString().Trim());
                itemDescs.Add(reader["ItemDescription"].ToString().Trim());
            }
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }
        finally
        {
            sqlConn.Close();   //NOTE: I HAVE A BREAKPOINT HERE FOR DUBUGGING
        }

        items = itemIDs.ToArray(typeof(string)) as string[];
        description = itemDescs.ToArray(typeof(string)) as string[];
        return true;
    }
}

This all works fine, but by setting a breakpoint where I said what I said, I noticed that the elements and the description of the class elements retain the allocated memory and elements between the execution of my program (the local asp dev server). Why is this memory not freed when the program ends (exiting the browser or stopping debugging mode)? Is there a way to manually free this memory and create a handle for a static class?

Answer 1

, , , - :

public static void Unload() {
    items = description = null;
}

Re " " - , . , ( IIS) .

Answer 2

, , WebDev . , . , (- ).