Polymorphic Type Support in SignalR Hubs

SignalR, a real-time communication library for .NET applications, introduces exciting new features. The article demonstrates the concept of polymorphic type support within SignalR Hubs.

Overview

Traditionally, SignalR Hub methods expected derived classes as input parameters. However, with the latest enhancements, Hub methods can now accept base classes, enabling more flexible and polymorphic scenarios. This enhancement simplifies code and promotes better design practices.

Implementation Example

Let’s explore an example using C#:

    using Microsoft.AspNetCore.SignalR;
    public class MyHub : Hub
    {
        public void ProcessPerson(JsonPerson person)
        {
            if (person is JsonPersonExtended)
            {
                // Handle JsonPersonExtended logic
            }
            else if (person is JsonPersonExtended2)
            {
                // Handle JsonPersonExtended2 logic
            }
            else
            {
                // Handle other cases
            }
        }
    }
    [JsonPolymorphic]
    [JsonDerivedType(typeof(JsonPersonExtended), nameof(JsonPersonExtended))]
    [JsonDerivedType(typeof(JsonPersonExtended2), nameof(JsonPersonExtended2))]
    private class JsonPerson
    {
        public string Name { get; set; }
        public Person Child { get; set; }
        public Person Parent { get; set; }
    }
    private class JsonPersonExtended : JsonPerson
    {
        public int Age { get; set; }
    }
    private class JsonPersonExtended2 : JsonPerson
    {
        public string Location { get; set; }
    }

Explanation

1. MyHub: A SignalR Hub that defines the ProcessPerson method. This method accepts a JsonPerson object, which can be either the base class or its derived types.

2. JsonPerson: The base class representing a person. It includes common properties such as Name, Child, and Parent.

3. JsonPersonExtended and JsonPersonExtended2: Derived classes that extend JsonPerson. They introduce additional properties (Age and Location, respectively).

Conclusion

By embracing polymorphism, SignalR Hubs become more versatile and adaptable. Developers can now handle diverse data structures efficiently, making real-time communication even more powerful.

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