Solve real coding problems
Problem When I open a C# project in Visual Studio, none of the references are loading. In the error list it says “The referenced component could not be found” for several references. Here’s a snippet showing just a few of the reference errors: The referenced component ‘System’ could not be found.The referenced component ‘Microsoft.CSharp’ could … Read more
In this article we’re going to create a queue in Amazon Simple Queue Service (SQS) using an AWS Stack template. Amazon SQS and Spring Series This article is part of a series: What is a message queue Message queues allow different parts of a system to communicate and process operations asynchronously. A producer sends a … Read more
In regex, capturing groups give you a way to save text and refer to it later. Capturing groups can be named, and referred to by their name. When they aren’t named, you refer to them by their index number. In this article, I’ll show how to use named capturing groups by solving the problem of … Read more
In this article, I’ll explain how to solve the Sock Merchant algorithm problem on HackerRank. Problem statement: You’re given an integer array and need to count the number of pairs of matching integers. The integers will be between 1 and 100. For example, [3,1,3] has one matching pair (the 3s match). Approach First, we know … Read more
You need to auto-increment your build numbers in order to easily tell which code you’re working with. In this article I’ll explain how to auto-increment your build numbers in Visual Studio. I’ll be using text templating to generate the Assembly Version. 1 – Choose a versioning scheme I’m going to be using the version scheme: … Read more
Problem You’re trying to debug a program with Visual Studio but Attach to Process does not work. Most likely you’re loading your code through some third-party process (like Excel), and when you try to use Attach to Process it simply doesn’t work. Solution Instead of trying to use Attach to Process, you can launch a … Read more
In this article, I’ll explain how to solve the Bit Counting algorithm challenge on Codewars. Problem statement: Given a 32-bit signed integer, how many set bits are there? Ex: The number 15 has four bits set. Approach How do I know if a bit is set? A bit can either be 0 or 1. A … Read more
The need to mock static methods in order to add a unit test is a very common problem. It’s often the case that these static methods are in third-party libraries. There are many utility libraries that are completely made up of static methods. While this makes them very easy to use, it makes them really … Read more
The BlockingCollection class is a blocking concurrent queue. It provides an implementation of the producer-consumer pattern. There are two parts to this pattern: BlockingCollection is thread-safe, which means it’s designed to be used by many threads at once. Here’s an example of using BlockingCollection with one consumer and two producers: Note: BlockingCollection.IsCompleted means the queue … Read more
Problem When you’re executing a CREATE/ALTER statement to create a procedure/view/function/trigger, you get one of the following errors: ‘CREATE/ALTER PROCEDURE’ must be the first statement in a query batch ‘CREATE VIEW’ must be the first statement in a query batch. ‘CREATE FUNCTION’ must be the first statement in a query batch. ‘CREATE TRIGGER’ must be … Read more
Problem I’m trying to use Selenium with the ChromeDriver and I’m running into the following exception: Unhandled Exception: OpenQA.Selenium.DriverServiceNotFoundException: The chromedriver.exe file does not exist in the current directory or in a directory on the PATH environment variable. The driver can be downloaded at http://chromedriver.storage.googleapis.com/index.html Solution The simplest solution is to install the Selenium.Chrome.WebDriver package: … Read more
You can use SQL Server query notifications to send push notifications to your code when data changes. This is an alternative to polling the database for changes. In this article, I’ll show how to configure this feature and work with it in the code. 1 – Enable Service Broker and configure permissions You need to … Read more
Events are an implementation of the observer pattern and consists of two parts: There are three simple steps to using events, which I’ll show below. 1 – Add an event field The first step is to add an event field to a class with the event keyword and a delegate type (such as the generic … Read more
A CheckedListBox is a list control with multiple checkboxes. This allows the user to check multiple boxes at once. You can also programmatically check items in the CheckedListBox and remove them. How can I can get all the values they selected? By looping through the CheckedListBox.CheckedItems collection. See the UI and Code examples below. UI … Read more
Imagine you’re in the middle of Millennium Park in Chicago. You want some coffee, but want a good deal on it. You open an app and see the nearest coffee shops offering deals to anyone with this app. How did this app know the distance from you to the coffee shops? This article will show … Read more
One day I decided to challenge myself by trying to implement multithreaded quicksort. I wanted to see how it would compare to the built-in Array.Sort() method. I came up with two algorithms that were 2-4x faster than Array.Sort(): After continuing to tinker, in attempts to further optimize, I came across the AsParallel().OrderBy() method (PLINQ). After … Read more
When working on a Windows Service project you may want to run it as a Console App so you can see what’s going on. If you try to run the service in Visual Studio you’ll get an error that says: “Cannot start service from the command line or a debugger. A Windows Service must first … Read more
TcpClient has no direct way to set the connection timeout. It doesn’t have any parameters that allow you to control it, and SendTimeout / ReceiveTimeout don’t apply to the initial connection. The way I control the connection timeout is by awaiting a Task.WhenAny() with TcpClient.ConnectAsync() and Task.Delay(). Task.WhenAny() returns when any of the tasks complete. … Read more
I often need to be able to run multiple threads and update the UI based on the results. For example, I may need to execute GET requests to 10 different endpoints concurrently, and then report their results in a datagrid as they come back. The problem is you can’t just update the UI from any … Read more
I recently came across a complex sorting problem that required sorting the data into groups, then further sorting the data within each group. I’ll explain this problem with a concrete example, and then I’ll show the SQL query I used to solve the problem. Let’s say we have orders, departments, and users. Users can be … Read more
Attributes are used to store additional info about a class/method/property. The attributes are read at runtime and used to change the program’s behavior. Here are a few examples of commonly used built-in attributes: In general, you should try to use built-in attributes when possible. When it makes sense, you can create your own custom attribute. … Read more
Problem When you try to pass in an attribute constructor parameter to a custom attribute, you get one of the following compiler errors: Error CS0181 Attribute constructor parameter has type ‘Color’ which is not a valid attribute parameter type Error CS0655 ‘Color’ is not a valid named attribute argument because it is not a valid … Read more
Problem Any time you try to use a Linq extension method (such as Select() to transform list elements) and you haven’t added ‘using System.Linq’, you’ll get a compiler error like this: Could not find an implementation of the query pattern for source type ‘Your Type’. ‘Select’ not found. In newer versions, the error looks like … Read more
Problem When you’re binding a control to a list of objects by adding a BindingList to a BindingSource, you get the following exception: System.InvalidOperationException: Objects added to a BindingSource’s list must all be of the same type. Here’s the code causing this: Solution Instead of adding the BindingList to the BindingSource with Add(), set BindingSource.DataSource … Read more
Problem You’re trying to use the ReportViewer control in Visual Studio but it’s not in the toolbox. Other symptoms: Solution Note: Tested in Visual Studio 2017 and Visual Studio 2019. The exact instructions may have slightly different steps depending on which version of VS you’re using. There are two different problems to solve. First, you … Read more
