a developer's notebook
C# 7.0 adds a number of new features and brings the focus on data consumption, code simplification and performance. Perhaps the most interesting feature is tuples, a finite ordered list of values, of possibly different types, which is used to bundle related values together without having to create a specific type to hold them. Tuples are very good for performance reasons, as you don’t…
A custom validation attribute allows you to create metadata, that you can use in the data model to validate data fields. In order to validate when a collection is null or empty, you may create a custom validation attribute, which returns false in case the object is null or empty.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | public class NotNullOrEmptyCollectionAttribute : ValidationAttribute { public override bool IsValid(object value) { var collection = value as ICollection; if (collection != null) { return collection.Count != 0; } var enumerable = value as IEnumerable; return enumerable != null && enumerable.GetEnumerator().MoveNext(); } } |
You can now decorate classes using this attribute, i.e.:
1 2 3 4 5 | public class CustomModel { [NotNullOrEmptyCollection] public IEnumerable<string> Recipients { get; set; } } |
Let’s assume that you have a WebAPI method test/validation, which:…
In order to sort a collection of objects based on another list that contains the proper order, we can create an extension method that performs a Join between these two collections and pass a func as innerKeySelector argument to allow us to sort this collection based on whatever key we want. Example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | // Object that we are going to use class Item { public int Id { get; set; } public string Name { get; set; } } // Initialize a collection of objects var items = new List<Item> { new Item {Id = 1, Name = "Item 1"}, new Item {Id = 3, Name = "Item 3"}, new Item {Id = 5, Name = "Item 5"}, new Item {Id = 2, Name = "Item 2"} }; // Sort items based on the following order of ids var sortedIds = new[] { 1, 2, 5, 3 }; // Sort items based on the following order of ids var sortedNames = new[] { "Item 1", "Item 5", "Item 3" }; var sortedById = items.SortBy(sortedIds, c => c.Id); var sortedByName = items.SortBy(sortedNames, c => c.Name); // Result { "sortedById": [ { "id": 1, "name": "Item 1" }, { "id": 2, "name": "Item 2" }, { "id": 5, "name": "Item 5" }, { "id": 3, "name": "Item 3" } ], "sortedByName": [ { "id": 1, "name": "Item 1" }, { "id": 5, "name": "Item 5" }, { "id": 3, "name": "Item 3" } ] } |
