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Articles about coding with C# in .NET projects.
Previously you had to install and enable .NET Analyzers if you wanted to use it. Now, when you create a new project, it’s already installed and enabled by default (but you may want to change its settings). There are two main scenarios: If .NET Analyzers is already installed When you create a new project targeting … Read more
You can use the ClassInitialize attribute on a method when you want to initialize something for all unit tests in a test class. This initialization method only runs once and is ran before any of the unit tests. Here’s an example of how to add ClassInitialize: Note: ClassCleanup is the opposite of ClassInitialize. It runs … Read more
Dapper makes your code difficult to unit test. The problem is that Dapper uses static extension methods, and static methods are difficult to mock out. One approach is to wrap the Dapper static methods in a class, extract out an interface for that wrapper class, and then dependency inject the wrapper interface. In the unit … Read more
I’ll show examples of using the pattern matching operators – ‘not’, ‘and’, ‘or‘ – with the is operator. These are nice syntax sugar that make conditional logic a bit easier to read. Note: ‘not’, ‘and’, ‘or’ were added in C# 9. ‘not’ operator Here’s an example of the not operator: This is checking if the … Read more
In this article I’ll show how to install and configure a Windows Service, query its status and properties, and then how to uninstall it. I’ll be using the command line utilities installutil.exe and sc.exe to install and configure the service. Add a service installer class to your Windows Service project In order to use installutil.exe … Read more
Problem When you’re using WinForms and click a DataGridView column header, you get an exception like this: Index was out of range. Must be non-negative and less than the size of the collection. This problem is caused by the column header “row” triggering a click event (such as CellContentClick) with event args containing RowIndex of … Read more
When you need to insert multiple rows into the database, consider doing a Bulk Insert instead of inserting one row at a time. Bulk Insertions are up to 20x faster than executing SQL Insert repeatedly. The simplest way to do a SQL Bulk Insert is by using the built-in SqlBulkCopy (from System.Data.SqlClient) with a DataTable. … Read more
Nested conditionals are a code smell because they make the code harder to understand. They tend to grow more and more complicated over time because developers will keep adding conditions and more levels of nesting. The deeper the nesting, the more time it’ll eventually take to refactor it. Code Smell: Nested conditionals.Definition: A conditional block … Read more
In a console app there are two ways to get commands: After getting a command, you have to parse it to figure out what code to execute. Typically commands have the following format: commandName -argumentName argumentValue. For example, take a look at this familiar git command: This is passing the command line arguments into the … Read more
The following code shows how to wait for user input in a Console App: When the user types something in and presses the Enter key, Console.ReadLine() will return what they typed. Console.ReadLine() vs Console.ReadKey() Console.ReadLine() waits for the user to press Enter, and then returns everything they typed in. Console.ReadKey() returns individual key presses. It … Read more
Most of the time System.Text.Json will get you want you want. You can pass in options to control JSON serialization and deserialization to a certain extent. But sometimes you’ll run into scenarios where you need to customize how it handles a specific type. This is where JsonConverter comes in. You can customize serialization / deserialization … Read more
When you use System.Text.Json.JsonSerializer to serialize an object that has a cycle, you get the following exception: System.Text.Json.JsonException: A possible object cycle was detected which is not supported. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 0. In .NET 6+, you can … Read more
A CheckedListBox allows the user to check one or more checkboxes. Sometimes you’ll want to be able to check the boxes programmatically. For example, you may want to allow the user to check or uncheck all boxes at once. Or perhaps you want to persist the values the user checked and load them later. To … Read more
SqlDataReader returns a DBNull object when a column is null. This isn’t the same as a C# null. You can check if the column is null by comparing it with DBNull.Value or by using SqlDataReader.IsDBNull(). Here’s an example showing these two ways of checking if a column is null: After checking if the column is … Read more
In this article I’ll show how to use the SqlDataReader ADO.NET class in two scenarios involving multiple result sets: I have a StreamingService database that has Movies, Shows, and Episodes tables (linked to the shows). First I’ll show the model classes I’m mapping the data into. Then I’ll show the two scenarios where I’m using … Read more
When you’re testing if two strings are equal, you can simply use Assert.AreEqual(). When you’re testing if a string contains a substring or a pattern, typically developers use Assert.IsTrue() with a substring method or regex. You should use StringAssert instead, because it gives better failure messages. Note: StringAssert is nice because it’s a built-in class. … Read more
You can add default method implementations (and constants) to interfaces (in C# 7+), like this: Note: The Log() method is converting the DateTime to a string with a custom format and including it with the logging message. This outputs the following: Microsoft’s stated purpose for this feature is that it allows you add methods to … Read more
Here’s how to serialize an object into XML using XmlSerializer: You must add the [Serializable] attribute to the class you want to serialize: Here’s an example of creating an Author object and feeding it to the serializer: This outputs the following XML: This example showed how to use XmlSerializer with all the default settings. In … Read more
An event handler is a method that is registered to listen to an event. When the event is invoked, the event handler method is called. You may be tempted to directly call the event handler to unit test it. It’s better to actually raise the event though, and then check the side effects of the … Read more
When you serialize a tuple to JSON, it uses the the underlying ValueTuple’s field names – Item1 and Item2. It doesn’t matter if you’re using a named tuple, it won’t use the names you specified in the tuple declaration. This behavior is the same with Newtonsoft and System.Text.Json. Here’s an example of serializing a named … Read more
When you are using reflection to call a method, you may run into this exception: System.Reflection.TargetParameterCountException: Parameter count mismatch. This exception is straightforward – you aren’t passing in the correct number of parameters to MethodInfo.Invoke(). This article shows three different cases where you might run into this exception when using reflection. Using reflection to invoke … Read more
To create a custom exception, create a subclass of the Exception class, like this: Then throw it just like you would any other exception, like this: It’s a good idea to call the base constructor from your constructor and pass in your custom error message. If this exception is unhandled, or if you are logging … Read more
.NET Core enables you to write cross-platform C# code. Sometimes you’ll want to do things differently depending on the OS you’re running in. You can use RuntimeInformation.IsOSPlatform() to figure out which OS you’re in. Here’s an example of using this to see if you’re running in Windows: Example – Loading a different native library depending … Read more
The purpose of parameterized tests is to eliminate duplicated tests. There are two ways to pass parameters into a parameterized test: the DataRow attribute and the DynamicData attribute. With DataRow, the problem is you can only pass in constants and arrays. You can’t pass in reference types. When you try to pass in reference types, … Read more
In SQL Server 2016, Microsoft added support for handling JSON data: The JSON API in SQL Server is well-suited for simple scenarios where you only need to do basic querying and manipulation. For advanced querying, the SQL Server JSON API gets complicated and hard to use, so you may want to look into other options. … Read more
