C# Pattern Matching On Generic Type Parameters

In C# 7.1, and enhanced further in later versions, pattern matching on generic type parameters allows you to test and work with the runtime type of a generic type parameter in a type-safe way using is, switch, or switch expressions.

C# Pattern Matching On Generic Type Parameters Example

The below is a basic example of pattern matching on generic type parameters.

using System;

class CSharpProgram

{

static void Main(string[] args)

{

// int

PrintTypeInfo(42);

// string

PrintTypeInfo("hello");

// double

PrintTypeInfo(3.14);

}

static void PrintTypeInfo<T>(T input)

{

// Pattern matching using type pattern

if (input is int number)

{

Console.WriteLine($"It's an int: {number}");

}

else if (input is string text)

{

Console.WriteLine($"It's a string: {text}");

}

else if (input is double d)

{

Console.WriteLine($"It's a double: {d}");

}

else

{

Console.WriteLine($"Unknown type: {input?.GetType().Name ?? "null"}");

}

Output

In above example:
- T is the generic type parameter
- At runtime, pattern matching checks if the actual object is of a certain type.
- If it matches, it casts and declares a variable (number, text, d) all in one.

Summary

Pattern matching on generic type parameters allows you to test and work with the runtime type of a generic type parameter in a type-safe way using is, switch, or switch expressions.

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