where T IMyInterface (interface constraint)

Context: The constraint where T : IMyInterface requires the type parameter to implement the specified interface. This allows calling the interface members on instances of T. Multiple interfaces can be combined.

Usage Example

using System;
using System.Collections.Generic;

public interface IIdentifiable
{
    int Id { get; }
    string Name { get; }
}

public class Product : IIdentifiable
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Customer : IIdentifiable
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Display<T> where T : IIdentifiable
{
    public void ShowIdentity(T item)
    {
        Console.WriteLine($"ID: {item.Id}, Name: {item.Name}");
    }
}

class Program
{
    static void Main()
    {
        var product = new Product { Id = 1, Name = "Laptop" };
        var customer = new Customer { Id = 100, Name = "Alice" };

        var display = new Display<IIdentifiable>();
        display.ShowIdentity(product);
        display.ShowIdentity(customer);
    }
}

Output console

dotnet run
ID: 1, Name: Laptop
ID: 100, Name: Alice

Important notes

You can impose multiple interfaces: where T : IInterface1, IInterface2.
The interface can be generic itself.

Real-world usage example

List<T> – Does not impose an interface, but Dictionary<TKey, TValue> indirectly uses IEquatable<TKey>.
See .NET docs on interface constraint.

where T IMyInterface (interface constraint)

Usage Example

Output console

Important notes

Real-world usage example

Related sections