Ef Select To New Dto With Icollections How To Get Data
We have used lists of objects, either numeric or based on e.g. Id like to use the EF entities already created, in this case Team has a navigation.So, now that we have learned through the previous article how to get data from the data source with LINQ and filter it with the Where() method, the next step could be to sort the data. It seems that do this I need to create a new DTO class and use a select. If I assume correctly, you must have a one-to-many relationship between ReleaseVersions and ReleaseNotes, which means that there should be a navigation property in the ReleaseVersion class referring to the collection of ReleaseNotes, enabling you to rewrite your code like this: var model DbContext.ReleaseVersions. An SQL query thats for sure We will have two List collections with 3 and 4.Accepted Answer. Why BotherLINQ: Sorting data: the OrderBy() & ThenBy() methodsDataSet ds null using (StudentDTO dto new Trying to figure out the.
For example, you may have a collection of BookDTOs contained in a LibraryDTO.List sortedNumbers = numbers.OrderBy(number => number).ToList() Today I added one new implementation of mapper and this one is using. Other DTOs may be contained or aggregated in the DTO. The fields contained in the DTO are usually primitive types such as strings, boolean, etc. Fortunately for us, LINQ has several easy-to-use methods for sorting data - let's try a basic example first: List numbers = new List()The Data Transfer Object 'DTO', is a simple serializable object used to transfer data across multiple layers of an application. Therefore, the ability to properly sort the data, once we have the data we need, is crucial. However, as we have previously talked about, your data source for LINQ operations might as well be an XML document or a database.
And of course, you can mix and match the OrderBy(), OrderByDescending(), ThenBy() and ThenByDescending() methods in whatever way you need: List sortedUsers = listOfUsers.OrderBy(user => user.Age).ThenByDescending(user => user.Name).ToList() We're mostly using the method-based syntax of LINQ in this tutorial, but as always, I will take one of the examples in the article and show you how it would look with the query syntax - here's the latest example, including a LINQ query syntax version: // Method syntaxList sortedUsers = listOfUsers.OrderBy(user => user.Age).ThenByDescending(user => user.Name).ToList() List sortedUsersQ = (from user in listOfUsers orderby user.Age ascending, user.Name descending select user).ToList() As you can see, the syntax is slightly different - the direction (ascending or descending) is specified directly after the field to order by (ascending is actually implicit, but I included it to show you the difference). Here's an example: using System New User() ,List sortedUsers = listOfUsers.OrderBy(user => user.Age).ThenBy(user => user.Name).ToList() Console.WriteLine(user.Name + ": " + user.Age + " years") Quite simple but very effective! You can even chain multiple ThenBy() method calls, in case your data is more complex than the data from our test case. But of course you can get your list of integers and strings sorted easily - that's a piece of cake! However, thanks to LINQ, it's pretty much just as easy to sort more complex objects. And of course you can do it just as easy with strings, as we'll see in the next example, but let's get the items in descending (from largest to smallest/from Z to A) order: List cityNames = new List()"Amsterdam", "Berlin", "London", "New York"List sortedCityNames = cityNames.OrderByDescending(city => city).ToList() Foreach (string cityName in sortedCityNames)We do the exact same thing as before, except that we use the OrderByDescending() method instead of the OrderBy() method.
And remember, just like any other LINQ method, the actual data source is not manipulated - instead, you get a sorted copy of the original data source, which you can work with. SummaryUsing the OrderBy() and ThenBy() methods (as well as their "descending" counterparts), you can easily get your data sorted just the way you want it. Of course, in the end, both queries will give you the same result.
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