protected virtual Expression VisitJoin(JoinExpression node)
{
Expression left = VisitSource(node.Left);
Expression right = VisitSource(node.Right);
Expression condition = Visit(node.Condition);
if (node.Left != left || node.Right != right || node.Condition != condition)
{
return new JoinExpression(node.Type, left, right, condition);
}
return node;
}
private Expression BindJoin(Type resultType, Expression outerSource, Expression innerSource,
LambdaExpression outerKey, LambdaExpression innerKey,
LambdaExpression resultSelector)
{
ProjectionExpression outerProjection = VisitSequence(outerSource);
ProjectionExpression innerProjection = VisitSequence(innerSource);
_map[outerKey.Parameters[0]] = outerProjection.Projector;
Expression outerKeyExpr = Visit(outerKey.Body);
_map[innerKey.Parameters[0]] = innerProjection.Projector;
Expression innerKeyExpr = Visit(innerKey.Body);
_map[resultSelector.Parameters[0]] = outerProjection.Projector;
_map[resultSelector.Parameters[1]] = innerProjection.Projector;
Expression resultExpr = Visit(resultSelector.Body);
var join = new JoinExpression(resultType, outerProjection.Source, innerProjection.Source,
Expression.Equal(outerKeyExpr, innerKeyExpr));
SourceAlias alias = GetNextAlias();
ProjectedColumns pc = ProjectColumns(resultExpr, alias, outerProjection.Source.Alias,
innerProjection.Source.Alias);
return new ProjectionExpression(
new SelectExpression(alias, pc.Columns, join, null),
pc.Projector
);
}
