ref to Cache

[filmar]

Hi!
I have some problem:
I want to ref to Cache, and this mwthod doesn`t work. Why?

public DataTable getBookData(ref DataTable dat)
{
dat = (DataTable)(Cache["temp"]);
return (dat);
}

Cache has DataTable in itself (checked)

[filmar]

one more question:

/// <summary>
/// This routine gets the book data from cache and reloads the cache if
/// required.
/// </summary>
///
/// <param name="context">Set to the current Http context</param>
///
/// <returns>DataTable containing book data from the cache</returns>
public static DataTable getBookData(HttpContext context)
{
DataTable bookData = null;

// get the book data from the cache
bookData = (DataTable)(context.Cache[CAC_BOOK_DATA]);

// make sure the data is valid
if (bookData == null)
{
// data is not in the cache so load it
bookData = loadBookDataInCache(context);
}
return (bookData);
} // getBookData
} // CH16CacheService

bookData is ref to cache or new variable with it`s own allocated space in memory (copy of data from cache)?