/// <summary>
/// Execute an aggregation query.
/// </summary>
/// <typeparam name="K"></typeparam>
/// <param name="keySelector">A Lambda expression which represents an accessor property of the field which shoule be aggregated.</param>
/// <param name="aggregateType">One of the <see cref="AggregateType">AggregateType</see> enum members.</param>
/// <returns>A single value, which represents the aggregate</returns>
/// <remarks>Before using this function, make shure, that your database product supports the aggregate function, as defined in aggregateType.
/// Polymorphy: StDev and Var only return the aggregate for the given class. All others return the aggregate for all subclasses.
/// Transactions: Please note, that the aggregate functions always work against the database.
/// Unsaved changes in your objects are not recognized.</remarks>
public object ExecuteAggregate <K>(LE.Expression <Func <T, K> > keySelector, AggregateType aggregateType)
{
ExpressionTreeTransformer transformer =
new ExpressionTreeTransformer(keySelector);
string field = transformer.Transform();
return(ExecuteAggregate(field, aggregateType));
}
internal Expression ToExpression(string expressionText, CompiledScope scope)
{
var tokens = Lexer.Tokenize(expressionText).ToArray();
var astNode = Parser.Parse(tokens);
var transformer = new ExpressionTreeTransformer(LanguageDefinition, scope);
return(astNode.Transform(transformer));
}
private void TryPropagate(Expression dominatedExpression, Expression original, Expression replacement)
{
ExpressionTreeTransformer ett = new ExpressionTreeTransformer(original, replacement);
ett.Visit(dominatedExpression);
}
private void TryPropagate(Expression dominatedExpression, Expression original, Expression replacement)
{
ExpressionTreeTransformer ett = new ExpressionTreeTransformer(original, replacement);
ett.Visit(dominatedExpression);
}
