private static void ReadCsvAsStrings(TextReader reader, out NamedList <string>[] columns, out DataAdaptor[] headers)
{
Debug.Assert(reader != null);
// Get the column names from the first line.
string firstline = reader.ReadLine();
if (firstline == null)
{
columns = null;
headers = null;
return;
}
List <string> names = CsvHelper.ReadCells(firstline);
int count = names.Count;
// Put the columns into lists of strings, and as we do so, maintain the collection of
// types it can be parsed into, and whether any entries are null.
columns = new NamedList <string> [names.Count];
headers = new DataAdaptor[names.Count];
for (int columnIndex = 0; columnIndex < columns.Length; columnIndex++)
{
columns[columnIndex] = new NamedList <string>(names[columnIndex]);
headers[columnIndex] = new DataAdaptor();
}
while (true)
{
string line = reader.ReadLine();
if (line == null)
{
break;
}
List <string> cells = CsvHelper.ReadCells(line);
if (cells.Count != count)
{
throw new FormatException();
}
for (int columnIndex = 0; columnIndex < count; columnIndex++)
{
string cell = cells[columnIndex];
if (String.IsNullOrEmpty(cell))
{
headers[columnIndex].IsNullable = true;
columns[columnIndex].Add(null);
}
else
{
DataAdaptor header = headers[columnIndex];
header.TryParse(cell);
columns[columnIndex].Add(cell);
}
}
}
}
/// <summary>
/// Creates a new frame table from a file of comma-separated values.
/// </summary>
/// <param name="reader">A reader positioned at the beginning of the file.</param>
/// <returns>A new data frame with data from the file.</returns>
/// <remarks>
/// <para>The column names are taken from the first line of the file.</para>
/// <para>The storage type of each column is inferred from the types of objects
/// encountered are the frame table is constructed.</para>
/// </remarks>
public static FrameTable FromCsv(TextReader reader)
{
if (reader == null)
{
throw new ArgumentNullException(nameof(reader));
}
NamedList <string>[] textColumns;
DataAdaptor[] headers;
ReadCsvAsStrings(reader, out textColumns, out headers);
NamedList[] columns = new NamedList[headers.Length];
for (int columnIndex = 0; columnIndex < columns.Length; columnIndex++)
{
DataAdaptor header = headers[columnIndex];
if (header.TypeCandidates.Count == 0)
{
columns[columnIndex] = textColumns[columnIndex];
}
else
{
TypeParser adaptor = header.TypeCandidates.First.Value;
NamedList column = adaptor.CreateStorage(textColumns[columnIndex].Name, header.IsNullable);
foreach (string textValue in textColumns[columnIndex])
{
if (textValue == null)
{
column.AddItem(null);
}
else
{
object value = adaptor.Parse(textValue);
column.AddItem(value);
}
}
columns[columnIndex] = column;
}
}
FrameTable frame = new FrameTable(columns);
return(frame);
}
private static void ReadCsvAsStrings(TextReader reader, out DataList <string>[] columns, out DataAdaptor[] headers)
{
if (reader == null)
{
throw new ArgumentNullException(nameof(reader));
}
string firstline = reader.ReadLine();
if (firstline == null)
{
columns = null;
headers = null;
return;
}
List <string> names = CsvHelper.ReadCells(firstline);
int count = names.Count;
columns = new DataList <string> [names.Count];
headers = new DataAdaptor[names.Count];
for (int columnIndex = 0; columnIndex < columns.Length; columnIndex++)
{
columns[columnIndex] = new DataList <string>(names[columnIndex]);
headers[columnIndex] = new DataAdaptor();
}
while (true)
{
string line = reader.ReadLine();
if (line == null)
{
break;
}
List <string> cells = CsvHelper.ReadCells(line);
if (cells.Count != count)
{
throw new FormatException();
}
for (int columnIndex = 0; columnIndex < count; columnIndex++)
{
string cell = cells[columnIndex];
if (String.IsNullOrEmpty(cell))
{
headers[columnIndex].IsNullable = true;
columns[columnIndex].Add(null);
}
else
{
DataAdaptor header = headers[columnIndex];
LinkedListNode <TypeAdaptor> adaptorNode = header.TypeCandidates.First;
while (adaptorNode != null)
{
if (!adaptorNode.Value.IsParsable(cell))
{
header.TypeCandidates.Remove(adaptorNode);
}
adaptorNode = adaptorNode.Next;
}
columns[columnIndex].Add(cell);
}
}
}
}
