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Articles about coding with C# in .NET projects.
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
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
You can use Directory.EnumerateFiles() (in System.IO) to search for files in a directory. This has many overloads, allowing you to specify exactly what you want. You can get all the files in a directory, get all files in all subdirectories, filter files by name (including extension), and filter by attributes. Here’s an example of getting … Read more
The simplest way to read a file is to use a high-level method in the .NET File API (in System.IO), such as File.ReadAllText(). These high-level methods abstract away the details of opening a file stream, reading it with StreamReader, and closing the file. Here’s an example of reading a text file’s content using File.ReadAllText(): Notice … Read more
