LINQ expression with generic property

Question

My question is related to this one: linq-expression-with-generic-class-properties

This time I would like to get newly created objects which have the id in common. Th

Answer 1

You need to build a new expression representing the condition and pass that to Where:

public static IEnumerable GetNew(IQueryable objects, TId id, DateTime date, Expression> idSelector)
    where T : class, ISyncable
{
    var paramExpr = Expression.Parameter(typeof(T));
    var idEqExpr = Expression.Equal(Expression.Invoke(idSelector, paramExpr), Expression.Constant(id));
    var createdPropExpr = Expression.Property(paramExpr, "CreatedDate");
    var gtExpr = Expression.GreaterThan(createdPropExpr, Expression.Constant(date));
    var andExpr = Expression.And(idEqExpr, gtExpr);

    var condExpr = Expression.Lambda>(andExpr, paramExpr);

    return objects.Where(condExpr);
}

EDIT: If you know that the idSelector is a property expression, you could extract the referenced property and create a new property expression instead of using Invoke:

var idProperty = (PropertyInfo)((MemberExpression)idSelector.Body).Member;
var idEqExpr = Expression.Equal(Expression.Property(paramExpr, idProperty), Expression.Constant(id));