Solve real coding problems
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
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
Problem When entering the sa password while installing SQL Server you get the following error: “The specified sa password does not meet strong password requirements.“ Solution If the computer is on a domain Not on a domain
When you have commas in your CSV fields, it creates a conflict with the field delimiting commas. In other words, you can’t tell which data belongs to which field. How you deal with this will depend on one question: is the field with the comma enclosed in quotes? Comma is enclosed in quotes Spreadsheet programs … Read more
I’ll show how to parse comma-separated integer values from app.config and load them into a HashSet for efficient lookups. First, take a look at the setting (retryStatusCodes) in app.config: To load and parse this setting from app.config, do the following: The following code shows how to do this: Note: You have to add a reference … Read more
