{"id":906,"date":"2021-07-19T19:55:49","date_gmt":"2021-07-19T19:55:49","guid":{"rendered":"https:\/\/woitech.eu\/blog\/?p=906"},"modified":"2021-07-21T18:33:03","modified_gmt":"2021-07-21T18:33:03","slug":"linq-ensure-that-all-items-have-the-same-parent-key","status":"publish","type":"post","link":"https:\/\/woitech.eu\/blog\/2021\/07\/19\/linq-ensure-that-all-items-have-the-same-parent-key\/","title":{"rendered":"LINQ: Ensure that all items have the same parent key"},"content":{"rendered":"\n

Why C# Geek post series?<\/h2>\n\n\n\n

I love programming and C#. I have been working with it for the last 15 years. While my roles and responsibilities have changed over this time, my passion for C# stayed at the same level, thus I decided to write a set of posts on my personal observations, experiences, and learnings.<\/p>\n\n\n\n

What to expect from this series?<\/strong>
Well, I will try to cover various aspects of working with C# and .NET, where I will try to avoid opinionated posts but rather focus on sharing findings and providing comparisons.<\/p>\n\n\n\n

LINQ: Ensure that all items have the same parent key<\/h2>\n\n\n\n

Recently I have encountered an interesting problem. There is a method processing in bulk the collection of items, however, it is only able to process them if all items belong to the same parent object. In order to ensure it is the case, the method in question validates the input collection using the following code:<\/p>\n\n\n\n

if (items.GroupBy(i => i.ParentKey).Count() > 1)\n    throw new InvalidOperationException( \/* ... *\/);<\/code><\/pre>\n\n\n\n
The presented code is perfectly fine and does the job. I know however that LINQ offers various extension methods allowing to achieve the same outcome, thus I got curious to explore them and find out which one would be best suitable for this particular scenario.<\/p>\n\n\n\n
Setting up BenchmarkDotNet<\/h3>\n\n\n\n
In order to compare the differences, I created a new project following guidelines from BenchmarkDotNet<\/a> overview page with Program<\/code> class:<\/p>\n\n\n\n
public class Program\n{\n    static void Main(string[] args) => BenchmarkRunner.Run(typeof(Program).Assembly);\n}<\/code><\/pre>\n\n\n\n
I created a class Item<\/code> with ParentKey<\/code> property:<\/p>\n\n\n\n
public class Item\n{\n    public string ParentKey { get; init; }\n}<\/code><\/pre>\n\n\n\n
Then, I created a base benchmark class that will contain all benchmark methods:<\/p>\n\n\n\n
[MemoryDiagnoser]\npublic abstract class BenchmarkBase\n{\n    private readonly IEnumerable<Item> _data;\n\n    protected BenchmarkBase()\n    {\n        _data = GetData().ToArray();\n    }\n\n    protected abstract IEnumerable<Item> GetData();\n\n    \/* Benchmark methods... *\/\n}<\/code><\/pre>\n\n\n\n
… followed by a few child classes that run these benchmarks against collections of 1000 items, where:<\/p>\n\n\n\n