Unit Testing 101: From Zero to Hero

Do you want to start writing unit tests? But, you don’t know where to start? Do you want to adopt unit testing in your team? I can help you.

If you’re a beginner or a seasoned developer new to unit testing, this is the place for you.

Write it

Write your first unit tests with MSTest It’s the starting point to write unit tests. No prerequisites needed.

Identify and fix these 4 common mistakes when writing your first unit tests. Learn one of these 4 naming conventions and stick to it.

When writing your unit tests, make sure you don’t duplicate logic in Asserts. That’s THE most common mistake on unit testing.

Improve it

How to write good unit tests shows two common issues when writing unit tests: complex setup scenarios and hidden test values.

Make sure to always write a failing test first.

Use Builders to create test data. And, learn how to write tests that use DateTime.Now.

Fake it

Learn what fakes are in unit testing. It shows the difference between stubs and mocks. Follow these tips for better stubs and mocks in C#.

Read how to create fakes with Moq, an easy to use mocking library.

If you find yourself using lots of fakes, take advantage of automocking with TypeBuilder and AutoFixture to write simpler tests.

Master it

Last but not least, read all tips of this series on Unit Testing Best Practices. As an example, see how to refactor a real-world test to follow some of those best practices. Deep into assertions, check how to write better assertions and how to write custom assertions.

If you want to practice writing some unit tests, check my Unit Testing 101 repository over on GitHub.

Happy testing!

Five LINQ Methods in Pictures

One of the best C# features is LINQ. I would say it’s the most distinctive C# feature. These are five of the most common LINQ method in pictures.

LINQ is the declarative, immutable, and lazy-evaluated way of working with collections in C#. Some frequently used LINQ methods are Where, Select, Any, GroupBy, and FirstOrDefault.

Let’s work with a list of our favorite movies. Let’s write a Movie class with a name, release year, and a rating.

var movies = new List<Movie>
{
    new Movie("Titanic", 1998, 4.5f),
    new Movie("The Fifth Element", 1997, 4.6f),
    new Movie("Terminator 2", 1991, 4.7f),
    new Movie("Avatar", 2009, 5),
    new Movie("Platoon", 1986, 4),
    new Movie("My Neighbor Totoro", 1988, 5)
};

1. Where

The Where method returns a new collection with only the elements that meet a given condition.

The Where method works like a filter on collections. Think of Where as a replacement for a foreach with an if in it.

Let’s filter our list of movies to keep only those with a rating greater than or equal to 4.5.

var favorites = movies.Where(movie => movie.Rating >= 4.5);

This query would be something like this,

We’re using arrows to display our LINQ queries. But, the output of a LINQ query is lazy-evaluated. It means the actual result of a LINQ query is evaluated until we loop through its result.

2. Select

The Select method applies a function to transform every element of a collection.

Let’s find only the names of our favorite movies.

var favorites = movies.Where(movie => movie.Rating >= 4.5)
                      .Select(movie => movie.Name);

This query would be,

3. Any

The Any method checks if a collection has at least one element matching a condition. Unlike Where and Select, Any doesn’t return a new collection, but either true or false.

Let’s see if we have watched movies with a low rating.

var hasBadMovies = movies.Any(movie => movie.Rating < 2);

This query would be,

4. GroupBy

The GroupBy method returns a collection of “buckets” organized by a key. Also, GroupBy transforms each bucket of elements.

Let’s count the films with the same rating.

var groupedByRating = movies.GroupBy(movie => movie.Rating,
                                    (rating, movies) => new
                                    {
                                        Rating = rating,
                                        Count = movies.Count()
                                    });

The second parameter of the GroupBy is a Func with the grouping key and the elements of each group as parameters.

This query would be,

5. First & FirstOrDefault

The First and FirstOrDefault methods return the first element in a collection or the first one matching a condition. Otherwise, First throws an exception, and FirstOrDefault returns the default value of the collection type.

Let’s find the oldest film we have watched.

var oldest = movies.OrderBy(movie => movie.ReleaseYear)
                   .First();

This query would be,

Voilà! These are five LINQ methods I use often: Where, Select, Any, Group, and FirstOrDefault. Of course, LINQ has more. But, you will get your back covered with these five methods.

To learn about LINQ and other methods, check my quick guide to LINQ. All you need to know to start working with LINQ, in 15 minutes or less. For more C# content, check C# Definitive Guide for a list of subjects every intermediate C# developer should know. And, my top 10 best C# features for other cool C# features.

Happy LINQ time!

Brent Ozar Mastering courses. My Review

This is an honest review of Brent Ozar Mastering courses. I finished all of them some months ago.

I couldn’t write this a couple of years ago. Working with databases was a subject I avoided at all costs. Even to the point where I traded database-related tasks with an ex-coworker at a past job.

Avoiding database concepts cost me painful lessons. Like the day I wrote a query with a function around a column in the WHERE and it almost took the server to its knees. That query was poorly written, and the table didn’t have good indexes. It ended up scanning the whole table. Arrgggg!

But, it changed a couple of years later while working with one of my clients. They asked me to investigate the performance of some critical parts of the app. And, I ended up Googling what to do to speed up SQL Server queries and compiling six SQL Server performance tuning tips I found.

In that search for performance tuning advice, I found Brent Ozar and his mastering courses. These are the three things I liked after taking them.

1. Realistic Labs and Workloads

As part of Brent’s courses, we work with a copy of the StackOverflow database. Yeap, the same StackOverflow we all know and use.

After every subject in each course, we have labs to finish. Labs with bad queries, no indexes, blocking issues, etc. For the last course, Mastering Server Tuning, we have an emergency to fix. A server is on fire, and we have to put down the fire and lay out a long-term fix.

Often, some labs have easier alternatives. Either focus on a particular issue or run a workload and assess the whole situation.

2. Constraints to Solve Labs

As we progress throughout the courses, we start to have constraints to solve the labs. For example, “no index changes allowed” or “only query-level fixes.”

But, the exercise I like the most is the “Let’s play being performance consultant.” We have to fix a workload under 30 minutes with as few changes as possible. The closest thing to a real-world situation. That’s from Mastering Server Tuning again. I would say that was my favorite course.

Of course, there are more courses. They’re four in total. There’s one course solely on indexes, another one about query tuning, one to fix parameter sniffing issues, and, my favorite, the one on server-level fixes. Each course sits on top of the previous ones.

3. Popular wisdom and guerilla tactics

All over the courses, Brent shares his experience as a consultant. I have these pieces of advice on my notes like “when working with clients.”

For example, he shares to build as few indexes as possible and provide rollback scripts for index creation, just in case. Also, to provide a prioritize list of actionable steps to make SQL Server fast.

Also, he shares personal anecdotes. Like the day he went to consult wearing jeans, and everybody at the place was wearing jackets and ties. That story didn’t have a happy ending for the company. But, I won’t tell you more.

Voilà! These are the three things I liked. My biggest lessons are to focus all tuning efforts on the top-most wait type and make as few changes as possible to take you across the finish line. Often, we start to push buttons and knobs expecting SQL Server to run faster without noticeable improvements. Making more harm than good.

I will take the second lesson to other parts of my work, even outside of performance tuning context. Focus on the few changes that make the biggest impact.

For more SQL and performance tuning content, check don’t use functions around columns in your WHEREs, what implicit conversions are and why you should care and just listen to index recommendations. I wrote some of these posts to share my learnings after taking all Brent’s courses.

Happy coding!

Monday Links: Blog, Error Messages and Recruiters

Toxic Culture Is Driving the Great Resignation

I have read a couple of times about the Great Resignation. I guess the world isn’t the place after the pandemic. And that is reflected in the job market too. “A toxic corporate culture is the single best predictor of which companies suffered from high attrition in the first six months of the Great Resignation.” Read full article

What’s in a Good Error Message?

I don’t know how many times I have debugged the “The given key was not present in the dictionary” error. In fact, I wrote two C# idioms to avoid exceptions when working with dictionaries. From the article, to write better error messages: give context, show the actual error, and tell how to mitigate it. Read full article

Why don’t I have a blog?

I have always heard: “start your own blog.” Well, I started my own blog…you’re reading it. But this is a post about the opposite: why not have a blog. The author points out is that posts only rephrase Reddit or StackOverflow’s comments. But, I learned from Show Your Work that nothing is completely original. We all have some sort of inspiration. And, precisely that, and our own voice make our blogs unique. Read full article

Learn By Wrapping

The best advice to learn something is to learn by doing. Finding project ideas is often difficult. Another TODO app, really? This article shares a learning activity: Write a wrapper for a library or an API you’re already familiar with. Instead of jumping to the documentation, start writing a wrapper in the language you want to learn. Read full article

Career Advice Nobody Gave Me: Never Ignore a Recruiter

These days, anyone with a LinkedIn profile and “Software engineer” in the headline is getting lots of spam messages and connection requests. I bet you already got a message between these lines: “Hi X, I have one company interested in your profile. Are you available for a quick call to share more details? Please, send me your CV at this email.”

This article shares a template to reply back to these spammy messages. If you use it, you will be asking for a company name, seniority, and compensation before starting any conversation. That would be enough feedback for recruiters too. Read full article

Voilà! Another five reads! Do you answer spammy messages or connection requests on LinkedIn? Do you have a template to answer recruiters? What strategies do you use to learn new programming languages?

Are you interested in unit testing? Check my Unit Testing 101 series. Don’t miss the previous Monday Links on Going solo, Making Friends and AutoMapper.

BugOfTheDay: Object definitions, spaces, and checksums

These days I was working with a database migration tool. This is what I learned after debugging an issue for almost an entire day.

In one of my client’s projects to create or update stored procedures, we use a custom migrator tool. A wrapper on top of DbUp. I’ve already written about Simple.Migrator, a similar tool.

To avoid updating the wrong version of a stored procedure we rely on checksums. Before updating a stored procedure, we calculate the checksum of its definition at the database using a command-line tool.

How to find object definitions in SQL Server?

By the way… To find the text of a stored procedure in SQL Server, use the OBJECT_DEFINITION() function with the object id of the stored procedure.

Like this,

SELECT OBJECT_DEFINITION(OBJECT_ID('dbo.MyCoolStoredProc'))
GO

Checksums and CREATE statements

With the checksum of the stored procedure to update, we write a header comment in the new script file. Something like,

/*
Checksum: "A-SHA1-HERE-OF-THE-PREVIOUS-STORED-PROC"
*/
ALTER PROC dbo.MyCoolStoredProc
BEGIN
  ...
END

To upgrade the database, the migrator compares the checksums of objects in the database with the checksums in header comments. If they’re different, the migrator displays a warning message and stops the upgrade.

Here comes the funny part. When I ran the migrator on my local machine, it always reported a difference. Even when I was grabbing the checksum from the migrator tool itself. Arrggg!

After debugging for a while and isolating the problem I found something. On the previous script for the same stored procedure, I started the script with CREATE OR ALTER PROC. There’s nothing wrong with that.

But, there’s a difference in the object definitions of a stored procedure created with CREATE and with CREATE OR ALTER.

CREATE PROC vs CREATE OR ALTER PROC

Let me show you an example. We’re creating the same stored procedure with CREATE and CREATE OR ALTER to see its object definition.

/* With just CREATE */
CREATE PROC dbo.test
AS
SELECT 1
GO

SELECT LEN(OBJECT_DEFINITION(OBJECT_ID('dbo.Test'))) AS Length, OBJECT_DEFINITION(OBJECT_ID('dbo.Test')) AS Text
GO

/* What about CREATE OR ALTER? */
CREATE OR ALTER PROC dbo.test
AS
SELECT 1
GO

SELECT LEN(OBJECT_DEFINITION(OBJECT_ID('dbo.Test'))) AS Length, OBJECT_DEFINITION(OBJECT_ID('dbo.Test')) AS Text
GO

Here’s the output.

Notice the length of the two object definitions. They’re different! Some spaces were making my life harder.

The migrator compared checksums of the object definition from the database and the one in the header comment. They were different in some spaces.

I made the mistake of writing CREATE OR ALTER, and the migrator didn’t take into account spaces in object names before creating checksums. I had to rewrite the previous script to use ALTER and recreate the checksums.

Parting thoughts

But, what’s in this story for you? We should create processes to prevent mistakes in the first place. Scripts to make sure developers commit the code formatted properly. Checks to avoid applying data migrations to the wrong environment. Extensions or plugins to follow naming conventions. Scripts to install the right tools and dependencies to run a project. Up to date documentation for internal tools.

Often, code reviews aren’t enough to enforce conventions. We’re humans, and we all make mistakes. And, the more code someone reviews in a session, the more tired he will get. And, the more reviewers we add, the less effective the process gets.

Voilà! That’s what I learned these days: read object definitions from SQL Server, polish my debugging skills and build processes around our everyday development practice.

For more SQL Server content, check how to do case sensitive searches, when to follow index recommendations and how to write constants in stored procedures.

Happy debugging!

Working with ASP.NET Core IDistributedCache Provider for NCache

As we learned last time, when I covered in-memory caching with ASP.NET Core, a cache is a storage layer between an application and an external resource (a database, for example) used to speed up future requests to that resource. In this post, let’s use ASP.NET Core IDistributedCache abstractions to write a data caching layer using NCache.

What’s NCache?

From NCache official page, “NCache is an Open Source in-memory distributed cache for .NET, Java, and Node.js applications.”

Among other things, we can use NCache as a database cache, NHibernate 2nd-level cache, Entity Framework cache, and web cache for sessions and responses.

NCache comes in three editions: Open Source, Professional, and Enterprise. The Open Source version supports up to two nodes and its cache server is only available for .NET Framework version 4.8. For a complete list of differences, check NCache edition comparison.

One of the NCache key features is performance. Based on their own benchmarks, “NCache can linearly scale to achieve 2 million operations per second with a 5-server cache cluster.”

How to install NCache on a Windows machine?

Let’s see how to install an NCache server on a Windows machine. For this, we need a Windows installer and have a trial license key. Let’s install NCache Enterprise edition, version 5.2 SP1.

After running the installer, we need to select the installation type from three options: Cache server, remote client, and Developer/QA. Let’s choose Cache Server.

Then, we need to enter a license key. Let’s make sure to have a license key for the same version we’re installing. Otherwise, we will get an “invalid license key” error. We receive the license key in a message sent to the email address we used during registration.

Next, we need to enter the full name, email, and organization we used to register ourselves while requesting the trial license.

Then, we need to select an IP address to bind our NCache server to. Let’s stick to the defaults.

Next, we need to choose an account to run NCache. Let’s use the Local System Account.

Once the installation finishes, our default browser will open with the Web Manager. By default, NCache has a default cache named demoCache.

Next time, we can fire the Web Manager by navigating to http://localhost:8251.

NCache’s official site recommends a minimum of two servers for redundancy purposes. But, for our sample app, let’s use a single-node server for testing purposes.

So far, we have covered the installation instructions for a Windows machine. But, we can also install NCache in Linux and Docker containers. And, we can use NCache as virtual machines in Azure and AWS.

How to add and retrieve data from an NCache cache?

Now, we’re ready to start using our NCache server from a .NET app. In Visual Studio, let’s create a solution with a .NET 6 “MSTest Test Project” and a class file to learn the basic caching operations with NCache.

Connecting to an NCache cache

Before connecting to our NCache server, we need to first install the client NuGet package: Alachisoft.NCache.SDK. Let’s use the latest version: 5.2.1.

To start a connection, we need the GetCache() method with a cache name. For our sample app, let’s use the default cache: demoCache.

Let’s start writing a test to add and retrieve movies from a cache.

using Alachisoft.NCache.Client;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace NCacheDemo.Tests;

[TestClass]
public class NCacheTests
{
    [TestMethod]
    public void AddItem()
    {
        var cacheName = "demoCache";
        ICache cache = CacheManager.GetCache(cacheName);

		// We will fill in the details later
    }
}

If you’re new to unit testing, start looking at how to write your first unit test in C# with MSTest.

Notice we didn’t have to use a connection string to connect to our cache. We only used a cache name. The same one as in the Web Manager: demoCache.

NCache uses a client.ncconf file instead of connection strings. We can define this file at the application or installation level. For our tests, we’re relying on the configuration file at the installation level. That’s why we only needed the cache name.

Adding items

To add a new item to the cache, we need to use the Add() and AddAsync() methods with a key and a CacheItem to cache. The key is an identifier and the item is a wrapper for the object to cache.

Every item to cache needs an expiration. The CacheItem has an Expiration property for that.

There are two basic expiration types: Absolute and Sliding.

A cached item with Absolute expiration expires after a given time. Let’s say, a few seconds. But, an item with Sliding expiration gets renewed every time it’s accessed. If within the sliding time, we don’t retrieve the item, it expires.

Let’s update our test to add a movie to our cache.

using Alachisoft.NCache.Client;
using Alachisoft.NCache.Runtime.Caching;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Threading.Tasks;

namespace NCacheDemo.Tests;

[TestClass]
public class NCacheTests
{
    private const string CacheName = "demoCache";

    [TestMethod]
    public async Task AddItem()
    {
        var movie = new Movie(1, "Titanic");
        var cacheKey = movie.ToCacheKey();
        var cacheItem = ToCacheItem(movie);

        ICache cache = CacheManager.GetCache(CacheName);
        // Let's add Titanic to the cache...
        await cache.AddAsync(cacheKey, cacheItem);

        // We will fill in the details later
    }

    private CacheItem ToCacheItem(Movie movie)
        => new CacheItem(movie)
        {
            Expiration = new Expiration(ExpirationType.Absolute, TimeSpan.FromSeconds(1))
        };
}

[Serializable]
public record Movie(int Id, string Name)
{
    public string ToCacheKey()
        => $"{nameof(Movie)}:{Id}";
}

Notice, we used two helper methods: ToCacheKey() to create the key from every movie and ToCacheItem() to create a cache item from a movie.

We used records from C# 9.0 to create our Movie class. Also, we needed to annotate it with the [Serializable] attribute.

Retrieving items

After adding items, let’s retrieve them. For this, we need the Get<T>() method with a key.

Let’s complete our first unit test to retrieve the object we added.

using Alachisoft.NCache.Client;
using Alachisoft.NCache.Runtime.Caching;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Threading.Tasks;

namespace NCacheDemo.Tests;

[TestClass]
public class NCacheTests
{
    private const string CacheName = "demoCache";

    [TestMethod]
    public async Task AddItem()
    {
        var movie = new Movie(1, "Titanic");
        var cacheKey = movie.ToCacheKey();
        var cacheItem = ToCacheItem(movie);

        ICache cache = CacheManager.GetCache(CacheName);
        await cache.AddAsync(cacheKey, cacheItem);

        // Let's bring Titanic back...
        var cachedMovie = cache.Get<Movie>(cacheKey);
        Assert.AreEqual(movie, cachedMovie);
    }

    private CacheItem ToCacheItem(Movie movie)
        => new CacheItem(movie)
        {
            Expiration = new Expiration(ExpirationType.Absolute, TimeSpan.FromSeconds(1))
        };
}

[Serializable]
public record Movie(int Id, string Name)
{
    public string ToCacheKey()
        => $"{nameof(Movie)}:{Id}";
}

Updating items

If we try to add an item with the same key using the Add() or AddAsync() methods, they will throw an OperationFailedException. Try to add a unit test to prove that.

To either add a new item or update an existing one, we should use the Insert() or InserAsync() methods instead. Let’s use them in another test.

using Alachisoft.NCache.Client;
using Alachisoft.NCache.Runtime.Caching;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Threading.Tasks;

namespace NCacheDemo.Tests;

[TestClass]
public class NCacheTests
{
    // Our previous test is the same
    
    [TestMethod]
    public async Task UpdateItem()
    {
        ICache cache = CacheManager.GetCache(CacheName);

        var movie = new Movie(2, "5th Element");
        var cacheKey = movie.ToCacheKey();
        var cacheItem = ToCacheItem(movie);
        // Let's add the 5th Element here...
        await cache.AddAsync(cacheKey, cacheItem);

        var updatedMovie = new Movie(2, "Fifth Element");
        var updatedCacheItem = ToCacheItem(updatedMovie);
        // There's already a cache item with the same key...
        await cache.InsertAsync(cacheKey, updatedCacheItem);

        var cachedMovie = cache.Get<Movie>(cacheKey);
        Assert.AreEqual(updatedMovie, cachedMovie);
    }

    // Rest of the file...
}

Notice we used the InsertAsync() method to add an item with the same key. When we retrieved it, it contained the updated version of the item.

There’s another basic method: Remove() and RemoveAsync(). We can guess what they do. Again, try to write a test to prove that.

How to use ASP.NET Core IDistributedCache with NCache?

Up to this point, we have NCache installed and know how to add, retrieve, update, and remove items.

Let’s revisit our sample application from our post about using a Redis-powered cache layer.

Let’s remember the example from that last post. We had an endpoint that uses a service to access a database, but it takes a couple of seconds to complete. Let’s think of retrieving complex object graphs or doing some computations with the data before returning it.

Something like this,

using DistributedCacheWithNCache.Responses;

namespace DistributedCacheWithNCache.Services;

public class SettingsService
{
    public async Task<SettingsResponse> GetAsync(int propertyId)
    {
        // Beep, boop...Aligning satellites...
        await Task.Delay(3 * 1000);

        return new SettingsResponse
        {
            PropertyId = propertyId,
            Value = "Anything"
        };
    }
}

Notice we emulated a database call with a 3-second delay.

Also, we wrote a set of extensions methods on top of the IDistributedCache to add and retrieve objects from a cache.

There were the extension methods we wrote last time,

using Microsoft.Extensions.Caching.Distributed;
using Newtonsoft.Json;

namespace DistributedCacheWithNCache.Services;

public static class DistributedCacheExtensions
{
    public static readonly DistributedCacheEntryOptions DefaultDistributedCacheEntryOptions
        = new DistributedCacheEntryOptions
        {
            AbsoluteExpirationRelativeToNow = TimeSpan.FromSeconds(60),
            SlidingExpiration = TimeSpan.FromSeconds(10),
        };

    public static async Task<TObject> GetOrSetValueAsync<TObject>(this IDistributedCache cache,
                                                                  string key,
                                                                  Func<Task<TObject>> factory,
                                                                  DistributedCacheEntryOptions options = null)
        where TObject : class
    {
        var result = await cache.GetValueAsync<TObject>(key);
        if (result != null)
        {
            return result;
        }

        result = await factory();

        await cache.SetValueAsync(key, result, options);

        return result;
    }

    private static async Task<TObject> GetValueAsync<TObject>(this IDistributedCache cache,
                                                              string key)
        where TObject : class
    {
        var data = await cache.GetStringAsync(key);
        if (data == null)
        {
            return default;
        }

        return JsonConvert.DeserializeObject<TObject>(data);
    }

    private static async Task SetValueAsync<TObject>(this IDistributedCache cache,
                                                     string key,
                                                     TObject value,
                                                     DistributedCacheEntryOptions options = null)
        where TObject : class
    {
        var data = JsonConvert.SerializeObject(value);

        await cache.SetStringAsync(key, data, options ?? DefaultDistributedCacheEntryOptions);
    }
}

Notice we used Newtonsoft.Json to serialize and deserialize objects.

NCache and the IDistributedCache interface

Now, let’s use a .NET 6 “ASP.NET Core Web App,” those extension methods on top of IDistributedCache, and NCache to speed up the SettingsService.

First, we need to install the NuGet package NCache.Microsoft.Extensions.Caching. This package implements the IDistributedCache interface using NCache, of course.

After installing that NuGet package, we need to add the cache into the ASP.NET dependencies container in the Program.cs file. To achieve this, we need the AddNCacheDistributedCache() method.

// Program.cs
using Alachisoft.NCache.Caching.Distributed;
using DistributedCacheWithNCache;
using DistributedCacheWithNCache.Services;

var (builder, services) = WebApplication.CreateBuilder(args);

services.AddControllers();
// We add the NCache implementation here...
services.AddNCacheDistributedCache((options) =>
{
    options.CacheName = "demoCache";
    options.EnableLogs = true;
    options.ExceptionsEnabled = true;
});
services.AddTransient<SettingsService>();

var app = builder.Build();
app.MapControllers();
app.Run();

Notice, we continued to use the same cache name: demoCache. And, also we relied on a Deconstruct method to have the builder and services variables deconstructed. I took this idea from Khalid Abuhakmeh’s Adding Clarity To .NET Minimal Hosting APIs.

Back in the SettingsService, we can use the IDistributedCache interface injected into the constructor and the extension methods in the DistributedCacheExtensions class. Like this,

using DistributedCacheWithNCache.Responses;
using Microsoft.Extensions.Caching.Distributed;

namespace DistributedCacheWithNCache.Services
{
    public class SettingsService
    {
        private readonly IDistributedCache _cache;

        public SettingsService(IDistributedCache cache)
        {
            _cache = cache;
        }

        public async Task<SettingsResponse> GetAsync(int propertyId)
        {
            var key = $"{nameof(propertyId)}:{propertyId}";
            // Here we wrap the GetSettingsAsync method around the cache logic
            return await _cache.GetOrSetValueAsync(key, async () => await GetSettingsAsync(propertyId));
        }

        private static async Task<SettingsResponse> GetSettingsAsync(int propertyId)
        {
            // Beep, boop...Aligning satellites...
            await Task.Delay(3 * 1000);

            return new SettingsResponse
            {
                PropertyId = propertyId,
                Value = "Anything"
            };
        }
    }
}

Notice, we wrapped the GetSettingsAsync() with actual retrieving logic around the caching logic in the GetOrSetValueAsync(). At some point, we will have the same data in our caching and storage layers.

With the caching in place, if we hit one endpoint that uses that service, we will see faster response times after the first call delayed by 3 seconds.

Also, if we go back to NCache Web Manager, we should see some activity in the server.

In this scenario, all the logic to add and retrieve items is abstracted behind the IDistributedCache interface. That’s why we didn’t need to directly call the Add() or Get<T>() method. Although, if we take a look at the NCache source code, we will find those methods here and here.

Voilà! That’s NCache and how to use it with the IDistributedCache interface. With NCache, we have a distributed cache server with few configurations and a dashboard out-of-the-box. Also, we can add all the caching logic into decorators and have our services as clean as possible.

To follow along with the code we wrote in this post, check my Ncache Demo repository over on GitHub.

To read more content, check my Unit Testing 101 series to learn from how to write your first unit tests to mocks.

I wrote this post in collaboration with Alachisoft, NCache creators.

Happy coding!