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When you’re working with a JSON array, you can deserialize it to a list like this: This deserializes all of the objects in the JSON array into a List<Movie>. You can use this list object like usual. Note: All examples will use System.Collections.Generic and System.Text.Json. I’ll exclude the using statements for brevity. Example – JSON … Read more
In order to send a file in a request with HttpClient, add the file into a MultipartFormDataContent object, and send this object as the request content. Here’s an example: This sends the following multipart/form-data POST request: In this article, I’ll explain a few details about MultipartFormDataContent, and show a few other file-sending scenarios. MultipartFormDataContent Add() … Read more
Query strings start with ‘?’ and have one or more key-value pairs separated by ‘&’. All characters except a-z, A-Z, 0-9 have to be encoded, including Unicode characters. When you use HttpClient, it automatically encodes the URI for you (internally, it delegates this task to the Uri class). This means when you include a query … Read more
The simplest way to convert a list to a dictionary is to use the Linq ToDictionary() method: This loops through the list and uses the key/element selector lambdas you passed in to build the dictionary. In this article, I’ll go into details about how to use ToDictionary() and show how to deal with duplicate keys. … Read more
There are two ways add request headers when using HttpClient: In this article, I’ll show examples of both ways to add request headers. Add an unchanging header for all requests Let’s say you’re adding an API Key header. It needs to be included in all requests and the value won’t change. To add this request … Read more
Dictionaries are unordered data structures. Key/value pairs aren’t stored in sorted order. When you want the Dictionary in sorted order, there are two simple options: I’ll show both options. Sort Dictionary with OrderBy() Use OrderBy() (from System.Linq) to sort the Dictionary by key or value. It returns the Dictionary’s KeyValuePairs in ascending sorted order. I’ll … Read more
Deconstructing a tuple means assigning its fields to several variables at once by using the deconstruction assignment syntax. This is also referred to as destructuring or tuple unpacking. Here’s an example of deconstructing a tuple into two variables: This outputs: Deconstructing the tuple assigns the fields (Item1 and Item2) to variables based on position. The … Read more
You can use tuples to contain multiple values and pass them around. By default, the tuple field names are unfriendly – Item1, Item2, etc… Instead of using these default names, you can name the tuple fields. Here’s an example of creating and using a named tuple: Meaningful names makes tuples easier to use. movieTuple.title is … Read more
When you try to execute a parameterized query with EF Core, you get the following exception: System.InvalidCastException: The SqlParameterCollection only accepts non-null SqlParameter type objects, not SqlParameter objects The error message is confusing because it’s not showing the full type names. This error means you’re using System.Data.SqlClient.SqlParameter, but EF Core only accepts Microsoft.Data.SqlClient.SqlParameter. Note: They … Read more
To use a table-valued parameter (TVP) with SqlCommand (ADO.NET), pass in a DataTable as a SqlDbType.Structured parameter, like this: I’ll show a full example, starting with creating a TVP type and then inserting it as a SqlDbType.Structured parameter as shown above. 1 – Create the TVP type in SQL Server To be able to pass … Read more
System.Text.Json doesn’t support serializing / deserializing multidimensional arrays. When you try, it throws an exception like this – System.NotSupportedException: The type ‘System.Int[,] is not supported. You have three options: In this article, I’ll show an example of how to create a custom JsonConverter that handles multidimensional arrays. In this example, I’ll specifically show how to … Read more
I wrote about how to add custom validation attributes. These are used for model validation on the server-side. You can also use these for client-side validation, which I’ll show in this article. 1 – Implement IClientModelValidator The first step is to implement the IClientModelValidator interface in the custom validation attribute class. This has a single … Read more
When you send a request to ASP.NET with a JSON body, you get the following exception: System.Text.Json.JsonException: The JSON value could not be converted to System.String. Path: $ | LineNumber: 0 | BytePositionInLine: 1. You can’t deserialize JSON to a string. You’re either using a string parameter with [FromBody] or your model has a string … Read more
Use the XElement class (from the Linq-to-Xml API) to parse XML and work with it in memory. You can use this to search for XML elements, attributes, and modify values. This is an alternative to deserializing to an object (which requires you to define a class that matches the XML structure). I’ll show examples of … Read more
XML elements can have attributes, which are key-value pairs. To read the attributes, use the XElement class (from the Linq-to-Xml API). There are two main methods for getting attributes: Once you have the attributes, use the XAttribute.Value property to read the attribute’s string value. Here’s an example of getting all elements named Movie and then … Read more
The simplest way to select a single row with Dapper is to use QuerySingleOrDefault() with a SELECT + WHERE query. You can pass in the parameters to specify which record to select and specify the model type. Here’s an example: The SQL query returns a single row from the Movies table and Dapper maps it … Read more
You can update records with Dapper by using Execute() with an UPDATE statement and passing in the parameters. Here’s an example: Dapper maps the properties from the param object to the query parameters (ex: it maps year to @year). You can pass in the parameters with an anonymous type (as shown above) or by passing … Read more
You can insert records with Dapper by using Execute() on an INSERT statement and passing in a model object. Here’s an example of inserting a single movie record: Notice that you can simply pass in an object (param: movie) and Dapper handles the tedious parameter mapping for you. It tries to map properties from the … Read more
You can delete records with Dapper by using Execute() with a DELETE statement and specifying the record ID as a parameter. Here’s an example: This deletes a single record from the Movies table. Delete multiple records When you’re deleting multiple records, you can efficiently execute a single DELETE statement with a WHERE clause including all … Read more
You can execute stored procedures with Dapper by specifying the name, parameters, and CommandType.StoredProcedure. Let’s say you have the following stored procedure (single parameter, returns movie rows): Here’s how to execute this stored procedure with Dapper and map its results to Movie objects: Use an output parameter To get a stored procedure’s output parameter, add … Read more
There are five main aggregate functions in SQL: COUNT(), SUM(), AVG(), MIN(), and MAX(). These calculate aggregate values for sets of rows. When you use them with GROUP BY, they calculate the aggregate values for each group. Let’s say you want to get movie streaming stats for each user. Here’s an example of using GROUP … Read more
GROUP BY groups rows based on one or more column and produces grouped rows. ORDER BY sorts rows. You can use these together to sort groups. There are two options you can use for sorting groups: I’ll show examples below. At the end, I’ll talk about how SQL Server may implicitly sort groups (and why … Read more
ASP.NET Core gives you a chance to gracefully shutdown your background services (such as cleaning up and/or finishing in-progress work). By default, you’re given a grand total of 5 seconds to shutdown all background services. If you need more time than this, there are a few ways to control the graceful shutdown time, which I’ll … Read more
When you’re using the Visual Studio debugger to step through your code, sometimes it’s useful to be able to step into the .NET source code. I had to do this recently to figure out why my ASP.NET Core code wasn’t behaving as expected. You can enable .NET source code debugging with the following steps: Now … Read more
StreamWriter buffers by writing data to an internal char array with a default size of 1024 (and a minimum size of 128). Once the buffer is full (or when you dispose the StreamWriter), it flushes the buffer to the underlying stream. You can change StreamWriter’s buffer size by passing in the bufferSize parameter. Here’s an … Read more
There are two ways to programmatically make a file read-only: Here’s an example showing both ways to make a file read-only: Using File.SetAttributes() is useful when you want to manage all of file’s attributes at once. FileAttributes is an enum flag, so you can use bitwise operations to add/remove multiple attributes at once. That’s why … Read more
When you want to set permissions for a directory (and its files/subdirectories), you can use DirectoryInfo.GetAccessControl() to get the directory’s security, add/modify/remove access control rules, and then use DirectoryInfo.SetAccessControl() to apply the changes. Access control rules are a complex combination of different settings. So before jumping into setting the permissions programmatically, I suggest taking a … Read more
The simplest way to delete a directory is by using Directory.Delete() (in System.IO). You specify the directory path (absolute or relative) and an optional parameter that tells it to delete everything in the directory. Here’s an example of how to use this to delete directories: Note: If you’re working with DirectoryInfo objects already, you can … Read more
You can use Directory.CreateDirectory() to create a directory at the specified path (absolute or relative), like this: This creates the directory if it doesn’t exist, otherwise it does nothing. That means you don’t need to check if the directory exists before calling Directory.CreateDirectory(). In this article, I’ll go into more details about using Directory.CreateDirectory(). CreateDirectory() … Read more
There are three ways to update a file’s content: Which option you pick depends on the file’s format and size. For example, if you’re writing to an existing CSV file, you’d append new lines to the end of the file. If you’re updating a JSON file, you’d read all the JSON content, make changes, then … Read more
