Generics

Generic Constraints

A generic constraint requires a type parameter to provide certain members.

Generic Constraints

GenericConstraints.cs 
using System;

interface INamed
{
    string Name { get; }
}

class Customer : INamed
{
    public string Name { get; }

    public Customer(string name)
    {
        Name = name;
    }
}

class Program
{
    static string Label<T>(T item) where T : INamed
    {
        return "name:" + item.Name;
    }

    static void Main()
    {
        string name = ;
        Customer customer = new Customer(name);
        string label = Label(customer);

        Console.WriteLine($"name={name}");
        Console.WriteLine($"label={label}");
    }
}

using System;

interface INamed
{
    string Name { get; }
}

class Customer : INamed
{
    public string Name { get; }

    public Customer(string name)
    {
        Name = name;
    }
}

class Program
{
    static string Label<T>(T item) where T : INamed
    {
        return "name:" + item.Name;
    }

    static void Main()
    {
        string name = ;
        Customer customer = new Customer(name);
        string label = Label(customer);

        Console.WriteLine($"name={name}");
        Console.WriteLine($"label={label}");
    }
}

using System;

interface INamed
{
    string Name { get; }
}

class Customer : INamed
{
    public string Name { get; }

    public Customer(string name)
    {
        Name = name;
    }
}

class Program
{
    static string Label<T>(T item) where T : INamed
    {
        return "name:" + item.Name;
    }

    static void Main()
    {
        string name = ;
        Customer customer = new Customer(name);
        string label = Label(customer);

        Console.WriteLine($"name={name}");
        Console.WriteLine($"label={label}");
    }
}
constraint A constraint limits which types can be used with a generic method or class.