Скачать или смотреть How to Fix the No implicit reference conversion Error in C# Generics

Discover the reasons behind the `No implicit reference conversion` error in C# generics and learn how to define your generic class correctly for better code structure.
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This video is based on the question https://stackoverflow.com/q/63659413/ asked by the user 'ChiliYago' ( https://stackoverflow.com/u/284560/ ) and on the answer https://stackoverflow.com/a/63659541/ provided by the user 'Artfunkel' ( https://stackoverflow.com/u/418362/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the No implicit reference conversion Error in C# Generics

When working with generics in C# , you might encounter an error that can be confusing at first glance. One common issue developers face is the message: "No implicit reference conversion from 'List QSO ' to 'List List QSO '". If this has happened to you, don’t worry—this post will guide you through understanding and resolving this problem.

The Problem: What’s Happening?

You are trying to create a generic class that accepts a List<T>, but you get an error when you attempt to instantiate it. Here’s the relevant code section that triggers the issue:

[[See Video to Reveal this Text or Code Snippet]]

Error Message Explained

When you attempt to create a new instance of MyTables with a List<QSO>, like this:

[[See Video to Reveal this Text or Code Snippet]]

You receive an error message that states:

[[See Video to Reveal this Text or Code Snippet]]

This error occurs because of the constraint you have placed on the generic parameter T. Let's break this down.

What’s Causing the Confusion?

Generic Constraint: The where T : List<T> constraint specifies that T must be a List of itself. This means the compiler is expecting T to be something like List<List<T>>, creating a recursive structure that doesn’t work with what you attempted to pass (List<QSO>).

The Solution: Correcting Your Generic Class

To resolve the issue, you need to modify your generic class definition to remove the self-referential constraint. Instead, you can simply allow T to be any type without constraints related to lists. Here’s an improved version of your class:

[[See Video to Reveal this Text or Code Snippet]]

How This Works

Flexibility: This modified class can now accept any type T, so you can instantiate it with a List<QSO> without issues.

Simplicity: The code is cleaner and avoids unnecessary complications.

Conclusion

Generics can initially seem intimidating, especially when you run into errors like No implicit reference conversion. However, understanding the constraints you've placed and how they affect the types you are working with can help clarify the situation. By adjusting your generic class definition to eliminate the restrictive constraint, you can easily create a class that handles lists of any type, solving the problem efficiently.

Now you can focus on building out your functionality rather than fixing type conversion errors. Happy coding!