/// <summary>
/// Computes the given expression on the current_rows that
/// pass the filter criteria.
/// </summary>
public object Compute (string expression, string filter)
{
// expression is an aggregate function
// filter is an expression used to limit rows
DataRow [] rows = Select (filter);
if (rows == null || rows.Length == 0)
return DBNull.Value;
Parser parser = new Parser (rows);
IExpression expr = parser.Compile (expression);
object obj = expr.Eval (rows [0]);
return obj;
}
internal void CompileExpression (string expression)
{
if (expression != String.Empty) {
if (AutoIncrement || Unique)
throw new ArgumentException ("Cannot create an expression on a column that has AutoIncrement or Unique.");
if (Table != null) {
for (int i = 0; i < Table.Constraints.Count; i++) {
if (Table.Constraints [i].IsColumnContained (this))
throw new ArgumentException (
String.Format (
"Cannot set Expression property on column {0}, because it is a part of a constraint.",
ColumnName));
}
}
Parser parser = new Parser ();
IExpression compiledExpression = parser.Compile (expression);
if (Table != null) {
if (compiledExpression.DependsOn (this))
throw new ArgumentException ("Cannot set Expression property due to circular reference in the expression.");
// Check if expression is ok
if (Table.Rows.Count == 0)
compiledExpression.Eval (Table.NewRow ());
else
compiledExpression.Eval (Table.Rows [0]);
}
ReadOnly = true;
_compiledExpression = compiledExpression;
} else {
_compiledExpression = null;
if (Table != null) {
int defaultValuesRowIndex = Table.DefaultValuesRowIndex;
if (defaultValuesRowIndex != -1)
DataContainer.FillValues (defaultValuesRowIndex);
}
}
}
/// <summary>
/// Gets an array of all DataRow objects that match
/// the filter in the order of the sort, that match
/// the specified state.
/// </summary>
public DataRow [] Select (string filterExpression, string sort, DataViewRowState recordStates)
{
if (filterExpression == null)
filterExpression = String.Empty;
IExpression filter = null;
if (filterExpression != String.Empty) {
Parser parser = new Parser ();
filter = parser.Compile (filterExpression);
}
DataColumn [] columns = _emptyColumnArray;
ListSortDirection [] sorts = null;
if (sort != null && !sort.Equals(String.Empty))
columns = ParseSortString (this, sort, out sorts, false);
if (Rows.Count == 0)
return NewRowArray (0);
//if sort order is not given, sort it in Ascending order of the
//columns involved in the filter
if (columns.Length == 0 && filter != null) {
ArrayList list = new ArrayList ();
for (int i = 0; i < Columns.Count; ++i) {
if (!filter.DependsOn (Columns [i]))
continue;
list.Add (Columns [i]);
}
columns = (DataColumn []) list.ToArray (typeof (DataColumn));
}
bool addIndex = true;
if (filterExpression != String.Empty)
addIndex = false;
Index index = GetIndex (columns, sorts, recordStates, filter, false, addIndex);
int [] records = index.GetAll ();
DataRow [] dataRows = NewRowArray (index.Size);
for (int i = 0; i < dataRows.Length; i++)
dataRows [i] = RecordCache [records [i]];
return dataRows;
}
public DataRow[] Select(string filterExpression, string sort, DataViewRowState recordStates)
{
if (filterExpression == null)
filterExpression = String.Empty;
DataColumn[] columns = _emptyColumnArray;
ListSortDirection[] sorts = null;
if (sort != null && !sort.Equals(String.Empty))
columns = ParseSortString (this, sort, out sorts, false);
IExpression filter = null;
if (filterExpression != String.Empty) {
Parser parser = new Parser ();
filter = parser.Compile (filterExpression);
}
Index index = FindIndex(columns, sorts, recordStates, filter);
if (index == null)
index = new Index(new Key(this,columns,sorts,recordStates,filter));
int[] records = index.GetAll();
DataRow[] dataRows = NewRowArray(index.Size);
for (int i = 0; i < dataRows.Length; i++)
dataRows[i] = RecordCache[records[i]];
return dataRows;
}