where T struct (value type)

Context: The constraint where T : struct requires the type parameter to be a non-nullable value type (int, double, bool, DateTime, enum, etc.). It excludes reference types (classes, interfaces, delegates). This constraint allows safe usage of value types.

Usage Example

using System;

public class NumericCalculator<T> where T : struct
{
    public T Zero => default(T); // default(T) = 0 for int, false for bool, etc.

    public T Add(T a, T b)
    {
        // For simplicity, use dynamic conversion (not ideal, but demonstration)
        dynamic da = a;
        dynamic db = b;
        return da + db;
    }
}

class Program
{
    static void Main()
    {
        var calcInt = new NumericCalculator<int>();
        Console.WriteLine(calcInt.Add(5, 3)); // 8

        var calcDouble = new NumericCalculator<double>();
        Console.WriteLine(calcDouble.Add(2.5, 1.2)); // 3.7

        // This does not compile: string is a reference type
        // var calcString = new NumericCalculator<string>();
    }
}

Output console

dotnet run
8
3.7

Important notes

• struct implies System.ValueType.
• Nullable value types (int?) are not allowed (because Nullable<T> is a struct but with special constraint).
• Useful for mathematical types or low-level buffers.

Real-world usage example

System.Nullable<T> – where T : struct guarantees that T is a value type.
See .NET docs on struct constraint.

Related sections

• 11.4 Constraints
• 11.4.2 where T : class