public bool Read()
{
ThrowIfDisposed();
var hasData = _reader.Read(_readerId);
if (hasData)
{
// If there is a row to read data for then get all of the values for it and, if we don't already have them, the names
// of the fields in the current result set. This will allow any requests for individual fields in the row (whether
// requested by field name or by index) to be returned from data in memory, rather than having to go back to the
// remote host every time (chatty WCF services can be slow). This has the disadvantage that every value from
// current row has been pulled in to memory and we might not need them all, but hopefully that's worth the
// trade-off (and, where performance is important, queries should only specify fields they want data for).
if (_currentColumnNamesLookupIfKnown == null)
{
var fieldNames = _reader.GetFieldNames(_readerId);
_currentColumnNamesLookupIfKnown = new Dictionary <string, int>(StringComparer.OrdinalIgnoreCase);
for (var i = 0; i < fieldNames.Length; i++)
{
if (!_currentColumnNamesLookupIfKnown.ContainsKey(fieldNames[i]))
{
_currentColumnNamesLookupIfKnown.Add(fieldNames[i], i);
}
}
}
// If any field names are repeated in the query (which can happen if the the same name is explicitly listed multiple times
// or there is a SELECT * and tables are joined that have columns with the same name) then the number of entries in the
// _currentColumnNamesLookupIfKnown dictionary will be fewer than the actual number of fields in the recordset. So,
// pass int.MaxValue as the maximumNumberOfValuesToRead argument in the GetValues call in order to get as many
// values are there are fields.
_valuesInCurrentRowIfKnown = _reader.GetValues(_readerId, int.MaxValue);
}
else
{
_valuesInCurrentRowIfKnown = null; // If there is no more data then there can be no values for the current row
}
return(hasData);
}
