public override ITabularFileAdapter CreateFileAdapter(IReadOnlyCollection <string> columnNames)
{
ITabularFileAdapter result =
new CommaDelimitedFileAdapter(
this.FilePath,
this.ProviderName,
columnNames);
return(result);
}
public async Task <IRow[]> Query(IReadOnlyDictionary <string, string> columns)
{
if (null == columns)
{
throw new ArgumentNullException(nameof(columns));
}
string query =
string.Format(
CultureInfo.InvariantCulture,
CommaDelimitedFileAdapter.QueryTemplate,
this.fileName);
if (columns.Any())
{
IList <KeyValuePair <string, string> > criteria = new List <KeyValuePair <string, string> >(columns.Count);
foreach (KeyValuePair <string, string> column in columns)
{
string criterionValue = CommaDelimitedFileAdapter.ComposeCriterion(column.Value);
KeyValuePair <string, string> criterion =
new KeyValuePair <string, string>(column.Key, criterionValue);
criteria.Add(criterion);
}
IReadOnlyCollection <string> filters =
criteria
.Select(
(KeyValuePair <string, string> item) =>
string.Format(
CultureInfo.InvariantCulture,
CommaDelimitedFileAdapter.FilterTemplate,
item.Key,
item.Value))
.ToArray();
string filter =
string.Join(CommaDelimitedFileAdapter.DelimiterFilter, filters);
query = string.Concat(query, CommaDelimitedFileAdapter.WhereClausePrefix, filter);
}
OleDbCommand commandQuery = null;
try
{
commandQuery = new OleDbCommand(query, this.connection);
DbDataReader reader = null;
try
{
reader = await commandQuery.ExecuteReaderAsync();
IList <IRow> rows = new List <IRow>();
while (reader.Read())
{
string rowKey = (string)reader[0];
Dictionary <string, string> rowColumns =
new Dictionary <string, string>(this.headers.Count - 1);
for (int indexColumn = 1; indexColumn < this.headers.Count; indexColumn++)
{
object columnValue = reader[indexColumn];
if (null == columnValue)
{
continue;
}
string value = columnValue.ToString();
if (string.IsNullOrWhiteSpace(value))
{
continue;
}
string columnHeader = this.headers.ElementAt(indexColumn);
rowColumns.Add(columnHeader, value);
}
IRow row = new Row(rowKey, rowColumns);
rows.Add(row);
}
IRow[] results = rows.ToArray();
return(results);
}
finally
{
if (reader != null)
{
reader.Close();
reader = null;
}
}
}
finally
{
if (commandQuery != null)
{
commandQuery.Dispose();
commandQuery = null;
}
}
}
