Optimize OrderBy Generic Method

Question

Here is my OrderBy method which includes concatenated column names. Can this be achieved more efficiently?

public static IQueryable<T> Sort<T>(this IQueryable<T> query, List<SortationDto> sortations)
 where T : BaseEntity
{
 sortations.ForEach(s =>
 {
 Expression value = null;
 ParameterExpression parameter = Expression.Parameter(query.ElementType, "item");
 // if sortation is a concatenation of two columns
 if (s.Concatenated.Count > 0)
 {
 Expression concat = null;
 s.Concatenated.ForEach(c =>
 {
 //get first property
 value = c.Column.Split('.').Aggregate((Expression)parameter, Expression.PropertyOrField);
 //if first property add as initial property
 if (concat == null)
 {
 concat = value;
 }
 else //else concatenate with first property
 {
 MethodInfo concatMethod = typeof(String).GetMethod("Concat", new Type[] { typeof(string), typeof(string), typeof(string) });
 value = Expression.Call(concatMethod, concat, Expression.Constant(" "), value);
 }
 });
 }
 else //else use one and only property
 {
 value = s.Column.Split('.').Aggregate((Expression)parameter, Expression.PropertyOrField);
 }
 //build lambda expression
 LambdaExpression predicate = Expression.Lambda(value, parameter);
 //define orderby method name based on current iteration of sortations
 string methodName = (sortations.IndexOf(s) == 0 ? "Order" : "Then") + (s.Direction == "asc" ? "By" : "ByDescending");
 //call method
 MethodCallExpression orderBy = Expression.Call(typeof(Queryable), methodName, new Type[] { query.ElementType, value.Type }, query.Expression, Expression.Quote(predicate));
 //add final expression to query
 query = query.Provider.CreateQuery<T>(orderBy);
 });
 return query;
}

• svick: What's the point of sorting concatenations when you're already supporting sorting by multiple columns?
• Sean Thorburn: Good point! I'll rework this method.

Answer 1

Removed unnecessary concatenation.

public static IQueryable<T> Sort<T>(this IQueryable<T> query, List<SortationDto> sortations)
 where T : BaseEntity
{
 List<SortationDto> combined = sortations.Where(s => s.Concatenated.Count == 0).Union(sortations.SelectMany(so => so.Concatenated)).ToList();
 combined.ForEach(s =>
 {
 ParameterExpression parameter = Expression.Parameter(query.ElementType, "item");
 Expression value = s.Column.Split('.').Aggregate((Expression)parameter, Expression.PropertyOrField);
 LambdaExpression predicate = Expression.Lambda(value, parameter);
 string methodName = (combined.IndexOf(s) == 0 ? "Order" : "Then") + (s.Direction == "asc" ? "By" : "ByDescending");
 MethodCallExpression orderBy = Expression.Call(typeof(Queryable), methodName, new Type[] { query.ElementType, value.Type }, query.Expression, Expression.Quote(predicate)); 
 query = query.Provider.CreateQuery<T>(orderBy);
 });
 return query;
}

Answer 2

Thanks for sharing your code! Works like a charm. Ended up using it with some adjustments and the extension method below. I pass the Sort objects in so that any parsing is done outside (separate the concern a bit).

public static IQueryable<TEntity> ApplySort<TEntity>(this IQueryable<TEntity> query, params Sort[] sorts)
 {
 if (sorts == null)
 return query;
 var applicableSorts = sorts.Where(s => s != null);
 if (!applicableSorts.Any())
 return query;
 applicableSorts
 .Select((item, index) => new { Index = index, item.PropertyName, item.Direction })
 .ToList()
 .ForEach(sort =>
 {
 ParameterExpression parameterExpression = Expression.Parameter(query.ElementType, "entity");
 var propertyExpression = Expression.Property(parameterExpression, sort.PropertyName);
 var sortPredicate = Expression.Lambda(propertyExpression, parameterExpression);
 string methodName = (sort.Index == 0 ? "Order" : "Then") + (sort.Direction == OrderDirection.Ascending ? "By" : "ByDescending");
 MethodCallExpression orderBy = Expression.Call(typeof(Queryable), methodName, new Type[] { query.ElementType, propertyExpression.Type }, query.Expression, Expression.Quote(sortPredicate));
 query = query.Provider.CreateQuery<TEntity>(orderBy);
 });
 return query;
 }