Try the following code. public static List<List<T>> Split<T>(IList<T> source) { return source .Select((x, i) => new { Index = i, Value = x }) .GroupBy(x => x.Index / 3) .Select(x => x.Select(v => v.Value).ToList()) .ToList(); } The idea is to first group the elements by indexes. Dividing by three has the effect of grouping them … Read more
First of all, IQueryable<T> extends the IEnumerable<T> interface, so anything you can do with a “plain” IEnumerable<T>, you can also do with an IQueryable<T>. IEnumerable<T> just has a GetEnumerator() method that returns an Enumerator<T> for which you can call its MoveNext() method to iterate through a sequence of T. What IQueryable<T> has that IEnumerable<T> doesn’t … Read more
See documentation List.Exists (Object method – MSDN) Determines whether the List(T) contains elements that match the conditions defined by the specified predicate. This exists since .NET 2.0, so before LINQ. Meant to be used with the Predicate delegate, but lambda expressions are backward compatible. Also, just List has this (not even IList) IEnumerable.Any (Extension method … Read more
The easiest way to solve the problem is to group the elements based on their value, and then pick a representative of the group if there are more than one element in the group. In LINQ, this translates to: var query = lst.GroupBy(x => x) .Where(g => g.Count() > 1) .Select(y => y.Key) .ToList(); If … Read more
You need to choose a Property to sort by and pass it as a lambda expression to OrderByDescending like: .OrderByDescending(x => x.Delivery.SubmissionDate); Really, though the first version of your LINQ statement should work. Is t.Delivery.SubmissionDate actually populated with valid dates?
I find that if you’re familiar with SQL syntax, using the LINQ query syntax is much clearer, more natural, and makes it easier to spot errors: var id = 1; var query = from post in database.Posts join meta in database.Post_Metas on post.ID equals meta.Post_ID where post.ID == id select new { Post = post, … Read more
People.Aggregate((curMin, x) => (curMin == null || (x.DateOfBirth ?? DateTime.MaxValue) < curMin.DateOfBirth ? x : curMin))
I recently did a very similar thing to make a type safe OnPropertyChanged method. Here’s a method that’ll return the PropertyInfo object for the expression. It throws an exception if the expression is not a property. public PropertyInfo GetPropertyInfo<TSource, TProperty>( TSource source, Expression<Func<TSource, TProperty>> propertyLambda) { Type type = typeof(TSource); MemberExpression member = propertyLambda.Body as … Read more
If your result set returns 0 records: SingleOrDefault returns the default value for the type (e.g. default for int is 0) FirstOrDefault returns the default value for the type If you result set returns 1 record: SingleOrDefault returns that record FirstOrDefault returns that record If your result set returns many records: SingleOrDefault throws an exception … Read more
Unless you simply need an array to meet other constraints you should use ToList. In the majority of scenarios ToArray will allocate more memory than ToList. Both use arrays for storage, but ToList has a more flexible constraint. It needs the array to be at least as large as the number of elements in the … Read more