C Sharp on bradleycarey.com

System.Text.Json.Serialization - Read Numbers from JSON strings

Thu, 17 Sep 2020 00:00:00 +0000

Lets say you are POSTing a json that looks like this:

{
  "someNumber": "123"
}

…to a server-side web api DTO that looks like this:

public class Stuff
{
    public int? SomeNumber { get; set; }
}

This thing will fail since the number in the json is quoted. It looks like System.Text.Json is adding JsonNumberHandling.AllowReadingFromString which will accomplish this once .NET 5.0 is finally released.

In the meantime, I wrote a custom converter which works with nullable ints.

StringJsonConverter.cs Link to heading

public class StringJsonConverter : JsonConverter<int?>
{
    public override int? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return reader.TokenType switch
        {
            JsonTokenType.Number => reader.GetInt32(),
            JsonTokenType.Null => null,
            JsonTokenType.String => int.TryParse(reader.GetString(), out var parsed) ? parsed : (int?)null,
            _ => throw new ArgumentOutOfRangeException(nameof(reader), reader.TokenType, "Cannot parse unexpected JSON token type.")
        };
    }

    public override void Write(Utf8JsonWriter writer, int? value, JsonSerializerOptions options)
    {
        if (value.HasValue)
        {
            writer.WriteNumberValue(value.Value);
        }
        else
        {
            writer.WriteNullValue();
        }
    }
}

Don’t forget to register it in one of the many ways you can do so:

FluentAssertions – Make null and empty strings be equivalent

Fri, 30 Jun 2017 00:40:04 -0500

FluentAssertions is my assertion library of choice when writing tests in C#. It is very easy to extend and has a ton of nice functionality out of the box.

Unfortunately, there seems to be no way to make a string be equivalent if it is both null and empty. Thankfully we can create our own using AssertionOptions.AssertEquivalencyUsing!

AssertionOptions.AssertEquivalencyUsing(options =>
  options.Using<string>(ctx => (ctx.Subject ?? string.Empty).Should().BeEquivalentTo(ctx.Expectation ?? string.Empty)).WhenTypeIs<string>()
);

Enum friendly names using attributes in C# ASP.NET MVC

Sun, 02 Aug 2015 14:58:24 -0400

Are you using enums in dropdowns or radiobuttons or something similar? Instead of hard coding display names, a way of reusing these names was coined in the MVC 3 days that involved decorating the enum with the DescriptionAttribute. Judging from posts on stack overflow, this was a very popular method.

When MVC 5 came out, it included new helpers for Enums (which was fantastic). However, MS used the typical DisplayAttribute (the DisplayAttribute.Name property to be exact) instead of the DescriptionAttribute to pull this off.

Using SQL Server Reporting Services (SSRS) in an ASP.NET MVC project

Mon, 08 Jun 2015 14:21:49 -0400

There are a handful of examples out on the internet on how to use SSRS from an ASP.NET website but all of the ones I came across seemed like hacks. They range from throwing an ASPX page with a ReportViewer control to complex JavaScript hacks. The following method is the one I have used for many years that adheres to the true MVC manner. This method connects to SSRS through the web service using Microsoft.Reporting.WebForms assembly.

Run-Length Encoding (RLE) in C#

Fri, 17 Aug 2012 14:47:10 -0400

I recently came across a file format that required usage of Run Length Encoding to handle. This involved writing methods for both decoding and encoding. Here are my results:

To decode, you just use a string and concatenate it with each numeric character that is encountered until you hit a non-numeric character. You use this string to figure out how many times you need to repeat the character:

public static string Decode(string toDecode)
{
    string coefficient = String.Empty;
    StringBuilder sb = new StringBuilder();

    foreach (char current in toDecode)
    {
        if (char.IsDigit(current))
            coefficient += current;
        else
        {
            if (coefficient == String.Empty)
                sb.Append(current);
            else
            {
                int count = int.Parse(coefficient);
                coefficient = String.Empty;
                for (int j = 0; j < count; j++)
                    sb.Append(current);
            }
        }
    }
    return sb.ToString();
}

Similarly, for encoding. I used a stringbuilder and a counter to figure out how many times a character was repeated then appended this to the stringbuilder:

Maze Solving Algorithms – Wall Follower

Wed, 15 Aug 2012 10:44:53 -0400

Maze solving algorithms are a well known area of research. Of these, one of the most well known solving strategies for simply connected mazes is the wall follower algorithm. This post will delve into the coding and implementation of such an algorithm (in C#, of course).

Window Minimize / Maximize Event (C# winforms)

Mon, 13 Aug 2012 09:58:34 -0400

If you are working in C# winforms and need to respond to window minimize and maximize events, it seems that winforms does not provide native event handlers. Such a feat is still very much possible through hooking into the Windows API.

The exact message you need to catch is WM_SYSCOMMAND and look for the SC_* messages:

SC_CLOSE 0xF060
SC_MAXIMIZE 0xF030
SC_MINIMIZE 0xF020
SC_RESTORE 0xF120

There are indeed more messages. Check the above link for a full list. Now for some sample code:

JSON resources in .NET

Fri, 03 Aug 2012 11:25:50 -0400

While working on Sprite Editor, I had to dig deep into the web in order to come up with a fast, lightweight method for the deserialization or parsing JSON files. The .NET 4 Framework does have a few methods to enable this functionality, but they are not very customizable or powerful.

Sprite Editor

Wed, 25 Jul 2012 23:01:56 -0400

Caustik wrote a neat program that lets sprites walk around on your desktop and perform all kinds of random interactions with each other. The program is networked as well, so if you throw a sprite off of your screen it actually goes to another user’s desktop.

Sprite Editor is what it sounds like – it is basically an editor to streamline creation of sprite *.spr and *.spi files. Create your own custom sprites then submit them on the sprites forums and all the users will be able to see your creations.

NGif C# Library with assorted bugfixes

Mon, 23 Jul 2012 23:05:24 -0400

NGif is a C# .NET library to handle encoding and decoding of animated GIFs. I found a use for it, but it had a few bugs. The very last two pixels were being rendered incorrectly as red and the transparency was not functioning properly. I have fixed these bugs, made a few minor improvements, and included writing to a Stream instead of to a File.

Links: