Fitogram.Knowable

Knowable<T>

Basic example

The Knowable<T> wrapper tells us if the enum is known:

public enum MyEnum
{
    Foo = 1,
}

Knowable<MyEnum> myKnowableEnum = new Knowable<MyEnum>();
myKnowableEnum = 1;

Console.WriteLine(myKnowableEnum.IsKnown); // True
Console.WriteLine(myKnowableEnum.Value); // Foo

myKnowableEnum = 2;

Console.WriteLine(myKnowableEnum.IsKnown); // False
Console.WriteLine(myKnowableEnum.Value); // Exception!

https://dotnetfiddle.net/IewleI

Use it with JSON

This is useful when trying to deserialize a string to an enum:

JsonSerializerOptions jsonSerializerOptions = new JsonSerializerOptions();
jsonSerializerOptions.Converters.Add(new Fitogram.Knowable.SystemTextJson.KnowableJsonConverter());
jsonSerializerOptions.Converters.Add(new System.Text.Json.Serialization.JsonStringEnumConverter());

// The JSON would come from an external application which might have enums your application does not know.
const string json = "{\"MyEnum\":\"Bar\"}";

MyDto myDto = JsonSerializer.Deserialize<MyDto>(json, jsonSerializerOptions);
Console.WriteLine(myDto.MyEnum.IsKnown); // False

if (myDto.MyEnum.IsKnown)
    Console.WriteLine(myDto.MyEnum.Value); // Use the value.
else
    throw new Exception("Unknown enum."); // Handle the issue gracefully.

public enum MyEnum
{
    Foo = 1,
}

public class MyDto
{
    public Knowable<MyEnum> MyEnum { get; set; }
}