ASP.NET Core – How to receive a request with text/plain content

When a request comes in and your action method has parameters, the framework tries to find the appropriate InputFormatter to handle deserializing the request data. There’s no built-in text/plain InputFormatter though, so when you send a request with text/plain content, it fails with a 415 – Unsupported Media Type error response. In this article, I’ll … Read more

ASP.NET Core – Only one parameter per action may be bound from body

When you have multiple parameters on an action method that are bound to the request body (implicitly or explicitly), you get the following fatal exception upon starting the web API: System.InvalidOperationException: Action ‘RecipeController.Post’ has more than one parameter that was specified or inferred as bound from request body. Only one parameter per action may be … Read more

ASP.NET Core – Four basic ways to receive parameters

There are four basic ways to receive parameters in an ASP.NET Core Web API: query strings, path parameters, request body, and request headers. I’ll show examples of these below. Query string parameters Let’s say you have two query string keys: name and servings. To add these query string parameters, add method parameters with names that … Read more

C# – How to send synchronous requests with HttpClient

In .NET 5 and above, you can use the HttpClient Sync API methods – Send() and ReadAsStream() – to send HTTP requests synchronously (as opposed to resorting to sync-over-async). Here’s the steps for doing this: Create an instance of HttpRequestMessage. Use the synchronous HttpClient.Send() to send the message. Use the synchronous HttpContent.ReadAsStream() to get the … Read more

C# – Configuring CsvHelper when the header names are different from the properties

When your CSV header names don’t match your property names exactly, CsvHelper will throw an exception. For example, if your header name is “title” and your property name is “Title”, it’ll throw an exception like: HeaderValidationException: Header with name ‘Title'[0] was not found. If you don’t want to (or can’t) change the names to match, … Read more

C# – Using CsvHelper when there’s no header row

In this article, I’ll show how to configure CsvHelper to map CSV fields to the right properties when there’s no header row. At the end, I’ll show the alternative approach of manually parsing in this scenario. Consider the following CSV data without a header row: Normally, CsvHelper maps fields to properties by matching column names … Read more

C# – ConfigurationSection.Get() returns null

When you use ConfigurationSection.Get() to load an object from appsettings.json, it returns null if the section doesn’t exist. Since you’re probably not expecting this to be null, this can lead to problems surfacing in unexpected places, such as getting a NullReferenceException: Note: If you’re using ASP.NET Core, you’ll be referring to the config via builder.Configuration … Read more

C# – Parsing a CSV file

In this article, I’ll show how to parse a CSV file manually and with a parser library (CsvHelper). Let’s say you have the following CSV file: To manually parse this, split each line with a comma and process the fields in the resulting string[] however you want. If there’s a header row, skip it (headers … Read more

C# – How to deconstruct an object

Deconstructing an object means assigning its properties to several variables with a one-liner using deconstruction assignment syntax (also referred to as destructuring or unpacking). To be able to deconstruct an object, it needs to have a Deconstruct() method. Some built-in types have this – tuples, dictionary key/value pairs, records – and you can add it … Read more

ASP.NET Core – Logging requests and responses

The simplest way to log requests/responses is to use the HTTP Logging middleware (added in v6). This is configurable, so you can make it suit your needs. If you need more control, you can add your own middleware instead. To use the HTTP Logging middleware, call UseHttpLogging() in your initialization code: Then add Microsoft.AspNetCore.HttpLogging.HttpLoggingMiddleware to … Read more

C# – Get rid of Nullable warnings when you’re checking for null in another method

When you’re calling a helper method that does null checking (throw-if-null), you’ll still get Nullable warnings in the calling code because the compiler doesn’t know you’re already doing null checking. Here’s an example: ThrowIfNull() throws an exception if employee is null, so you know for sure that it won’t be null in the rest of … Read more

C# – Ignore null properties during JSON serialization

By default, null properties are included during JSON serialization like this: There are two ways to ignore null properties: In this article, I’ll show examples of these two ways to ignore null properties. I’ll show how to do it with System.Text.Json and Newtonsoft. Ignore null properties with System.Text.Json Use JsonIgnoreCondition.WhenWritingNull to ignore null properties. You … Read more

How to set multiple startup projects in Visual Studio

Since VS2019, you can set multiple startup projects in the solution’s properties. This is useful when you have multiple projects in the same solution that you want to start at the same time (with or without debugging). Before this, you’d have to set a project as the startup project, start it, then repeat with all … Read more

C# – Ignore the Nullable CS8618 warning in DTO classes

When you have the Nullable Reference Types feature (Nullable for short) enabled, one of the warnings you’ll run into is the following: CS8618 Non-nullable property X must contain a non-null value when exiting constructor. This warning doesn’t make sense in a very common scenario: You can just ignore the warning when it applies to DTOs. … Read more

C# – How to treat warnings like errors

Warnings are easy to ignore and forget about, which isn’t good. They point out potential problems that you might want to fix. To make it easier to pay attention to warnings, you can treat them like errors. You can choose which warnings to treat like errors by using settings in the project file. There are … Read more

C# – Nullable Reference Types feature basics

The main purpose of the Nullable Reference Types (NRT) feature is to help prevent NullReferenceExceptions by showing you compiler warnings. You can make a reference type nullable (ex: Movie? movie) or non-nullable (ex: Movie movie). This allows you to indicate how you plan on using these references. The compiler uses this info while analyzing actual … Read more

C# – How to use JsonNode to read, write, and modify JSON

When you don’t want to create classes for JSON (de)serialization, one option is to use JsonNode. This allows you work with JSON as a mutable DOM that consists of JsonNode objects (JsonObject, JsonArray, JsonValue). You can use it to read, write, and modify JSON. Here’s an example. Let’s say you have the following JSON that … Read more

C# – Filter a dictionary

The simplest way to filter a dictionary is by using the Linq Where() + ToDictionary() methods. Here’s an example: Note: You can use the Dictionary constructor (new Dictionary<string, int>(filterList)) instead of ToDictionary() if you prefer. This produces a new dictionary with the filtered item: Where() produces a list (actually an IEnumerable) of KeyValuePair objects. Most … Read more

C# – Change a dictionary’s values in a foreach loop

In .NET 5 and above, you can directly change a dictionary’s values in a foreach loop. Here’s an example: This outputs the following: You couldn’t do this before .NET 5, because it would invalidate the enumerator and throw an exception: InvalidOperationException: Collection was modified; enumeration operation my not execute. Instead, you’d have to make the … Read more