How to make an array flexible? [closed]

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  public List<int> GetCounts(string connectionstring)
    {
        List<int> results = new List<int>();
        string sqlStmt = "SELECT DISTINCT COUNT(Grouping) from Attendance";

        using (SqlConnection conn 开发者_Python百科= new SqlConnection(@"Data Source=localhost\SQLEXPRESS;Initial Catalog=PSeminar;Integrated Security=true;Trusted_Connection=Yes;MultipleActiveResultSets=true"))
        using (SqlCommand cmd = new SqlCommand(conn,sqlStmt))
        {
            conn.Open();
            using (SqlDataReader rdr = cmd.ExecuteReader())
            {
                while (rdr.Read())
                {
                    int count = rdr.GetInt32(0);

                    results.Add(count);
                }
                rdr.Close();
            }
            conn.Close();
        }
        return results;
    }

Currently I have this code, I want the array to be flexible, meaning if i have more than two items in the database the array will be automatically updated. The above sql statement will retrieve the items that i want to put in the array above. If the sql statement result has more than 2 items i want the array to be updated automatically.

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If you want to retrieve an arbitrary number of items from the database, I would suggest the List<T> construct over an array.

Try this:

public List<int> GetCounts(string connectionString)
{
   List<int> results = new List<int>();

   string sqlStmt = "SELECT DISTINCT COUNT(Grouping) from Attendance";

   using(SqlConnection conn = new SqlConnection(connectionString))
   using(SqlCommand cmd = new SqlCommand(sqlStmt, conn))
   {
      conn.Open();

      using(SqlDataReader rdr = cmd.ExecuteReader())
      {
          while(rdr.Read())
          {
              int count = rdr.GetInt32(0);  // read item no. 0 from the reader, as INT

              results.Add(count);
          }  

          rdr.Close();
      }

      conn.Close();
   }

   return results;
}

and then you could call this method like this:

string connStr = @"Data Source=localhost\SQLEXPRESS;Initial Catalog=PSeminar;Integrated Security=true;Trusted_Connection=Yes;";

List<int> counts = GetCounts(connStr);

and you get back a list of all your counts - as many as there are - no dirty array hacks or anything necessary!

The List<T> construct is very flexible, too - you can have a List<string> or a list of any .NET type, really - you can build your own types (e.g. a class consisting of ten properties) and then have a list of that class type. Generics are cool! :-)

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Use FieldCount property of SqlDataReader to create an array. You can also use SqlDataReader.GetValues(object[]) method to populate an array of objects with column values in current row.

Hope it helps you.