How Can I Create Type-Safe Discriminated Unions in C#?

Discriminated Unions in C#

A discriminated union is a data structure that can store values of multiple different types. Unlike traditional unions in C, discriminated unions enforce type safety at compile time.

Problem Statement

The original question presents a problem where the author wants to create a data structure that can store values of different types, but with enforced type checking. The author attempts to implement a solution using a custom Union class, but it lacks compiler-enforced type safety.

Solution

The solution provided in the answer section addresses the type safety issue by using a type-safe union implementation. This implementation defines a base class Union3 that represents the discriminated union, and three nested classes Case1, Case2, and Case3 that represent the different cases of the union.

The Match method of the base class takes three functions as arguments, each corresponding to a different type that the union can hold. When calling Match, the appropriate function is executed based on the actual type of the value stored in the union.

Implementation Details

The nested classes Case1, Case2, and Case3 are used to encapsulate the values of their respective types. The constructor of the base class is made private to prevent external classes from inheriting from it.

Usage

The provided example demonstrates how to use the type-safe union to store values of different types and match them based on their actual types. The Match method allows for type-safe extraction of the union's value.

Conclusion

This solution provides a type-safe implementation of a discriminated union in C#. It eliminates the need for manual type checking and ensures that the code correctly handles the different types stored in the union.

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