Can You Have an Unknown Data Type in a Dotnet Generics Code?


Scott Campbell

Can You Have an Unknown Data Type in a Dotnet Generics Code?

When working with C# and dotnet, generics are a powerful tool that allows you to write reusable code. By using generics, you can create classes, methods, and data structures that can work with different types of data without sacrificing type safety.

However, there may be cases where you need to work with an unknown data type in your generics code. Can this be done? Let’s explore this topic further.

What are Generics?

Generics were introduced in C# 2.0 and provide a way to define classes, interfaces, and methods that can work with different data types without sacrificing type safety. Instead of specifying the actual types at compile-time, generics allow you to use type parameters that will be replaced with specific types when the code is compiled.

The Benefits of Using Generics

  • Code Reusability: Generics allow you to write code that can be reused across different data types. This reduces code duplication and improves maintainability.
  • Type Safety: With generics, the compiler performs type checking at compile-time, ensuring that only compatible types are used with your generic code.
  • Performance: Generics provide better performance compared to non-generic alternatives like using object. This is because generics avoid boxing and unboxing operations.

The Known Data Type Scenario

In most cases, when working with generics, you’ll know the data type beforehand. For example, if you’re creating a generic class for a stack data structure called Stack<T>, you’ll know the type of data that will be stored in the stack, such as int, string, or Person.

public class Stack<T>
    private List<T> items = new List<T>();

    public void Push(T item)

    public T Pop()
        if (items.Count == 0)
            throw new InvalidOperationException("Stack is empty");

        T item = items[items.Count - 1];
        items.RemoveAt(items.Count - 1);
        return item;

The Unknown Data Type Scenario

But what if you don’t know the data type beforehand and still want to use generics? Is it possible to have an unknown data type in your generics code?

The short answer is no. Generics require you to specify the types at compile-time, so you cannot create a generic class or method without knowing the data type.

Workarounds for Unknown Data Types

While you cannot have an unknown data type directly in your generics code, there are workarounds you can use depending on your requirements:

1. Using Interfaces or Base Classes

If you have a set of known types that share a common interface or base class, you can use that interface or base class as the type parameter in your generic code. This allows you to work with different types that implement the same interface or derive from the same base class.

public interface IMyInterface
    // Interface members..

public class GenericClass<T> where T : IMyInterface
    // Generic class implementation.

2. Using Reflection

If you truly don’t know the data type at compile-time, you can use reflection to work with unknown types. Reflection allows you to inspect and manipulate types dynamically at runtime. While this approach can be more complex and less performant, it provides the flexibility to work with unknown data types.

public class GenericClass
    public void DoSomething(object unknownObject)
        Type objectType = unknownObject.GetType();

        // Perform actions based on the type.


In conclusion, while you cannot have an unknown data type directly in your generics code, there are various workarounds available depending on your requirements. By using interfaces or base classes as type parameters or leveraging reflection, you can still achieve flexibility and reusability in your code.

Generics are a powerful feature of C# and dotnet that allow you to write flexible and reusable code. Understanding how to work with known and unknown data types in generics is essential for writing efficient and maintainable code.

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