Q: ASP.NET equivalent of this PHP code (arrays)? I am mainly programming in PHP, but for my school project I have to use ASP.NET(C#). Now I have this code which works in PHP:
$Data = array();
while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
    $date = strtotime($row["Date"])*1000;
    $Data[] = array($date, $row["Data"]);
}



*

*As you can see it's a 2D array, which is expanding, but the inner array always has two parameters. Now I have searched on the web and haven't found how to declare a expanding array in ASP.NET(C#).

*Is there a replacement for strtotime in aspx?

A: Given it's now C# and the datatypes should come across through the reader, the following should work:
// use a struct to store your retrieved information
public struct Details
{
  DateTime date;
  Object data;

  public Details(DateTime Date, Object Data)
  {
    date = Date;
    data = Data;
  }
}

// use List<T> to define a dynamically-sized list
List<Details> dataArray = new List<Details>();
while (reader.Read()) // query the database
{
  // add the information to the list as we iterate over it
  dataArray.Add(new Details(reader.GetDateTime("Date"),reader["Data"]));
}

// your new expansive array: dataArray.ToArray();
// converting an object to datetime: Convert.ToDateTime();

This also assumes you're using a SqlDataReader (though you could use almost anything to retrieve the information from SQL).

Update
Given the comments below, the information is retrieved from a database and then output to JSON. Because of the new requirement I am going to change the store format a bit. This gives the flexibility to continue using the JavaScriptSerializer while outputting to a format javascript can understand.
// make a list we can use
List<Object[]> details = new List<Object[]>();

// populate the data
using (SqlConnection connection = new SqlConnection("<connection string>"))
{
    SqlCommand command = new SqlCommand("<query string>");
    SqlReader reader = command.ExecuteReader();

    .. go through the database
    while (reader.Read())
    {
      DateTime date = reader.GetDateTime("Date");
      Double data = reader.GetDouble("Data");

      // convert the datetime to unix time
      // http://www.epochconverter.com/
      var epoc = (date.ToUniversalTime().Ticks - 621355968000000000) / 10000000;

      details.Add(new Object[]{ epoc, data });
    }
}

// Now we serialize
JavaScriptSerializer serializer = new JavaScriptSerializer();
String result = serializer.Serialize(details.ToArray());

And here's what I receive from result (for format anyways):
[
  [1297627668,0.7],
  [1297714068,1.1],
  [1297800468,0.1],
  ...
]


A: First, how are you getting the data from the SQL database?  I'll assume that you're getting it as a collection of DataRow objects.
For storing the data, I would suggest using a list of tuples, as shown below.
List<Tuple<DateTime, string>> Data = new List<Tuple<DateTime, string>>();
// Somehow get a collection of rows into a results object
foreach (DataRow row in results)
{
    DateTime dt = DateTime.Parse(row["Date"]);
    Data.Add(new Tuple<DateTime, string>(dt, row["Data"]));
}

You can then access items in the list by index, and the individual fields as Item1 and Item2:
DateTime dt = Data[0].Item1;
string itemData = Data[0].Item2;

