Le Thanh Hung's blog

This is a typical non-generic method :

void AddMultiple(List<Customer> customers, params Customer[] values)
{
    foreach (Customer value in values)
    {
        customers.Add(value);
    }
}

In order to add mutiple customer into List :

List<Customer> customers = new List<Customer>();
AddMultiple(customers, new Customer(), 
    new Customer(), new Customer());

However, the method above only works with type . To have it work
with any List , the method must be written as a generic method.
A generic method has one or more type parameters specified in <
and > delimiters after the method name :

void AddMultiple<T>(List<T> customList, params T[] values)
{
    foreach (T value in values)
    {
    customList.Add(value);
    }
}

List<int> listInteger = new List<int>();
AddMultiple<int>(listInteger, 1, 2, 3, 4);

List<Customer> customers = new List<Customer>;
AddMultiple<Customer>(customers, 
               new Customer(),
                new Customer(),
            new Customer(),
            new Customer());

In the example above, since the first regular argument is type List
listInteger, and the subsequent arguments are of type int 1, 2, 3 ,
4 the compiler can reason that the type parameter must be int. Thus,
we can use shorter syntax without specifying the type parameter
(<int>) :

List<int> listInteger = new List<int>();
AddMultiple(listInteger, 1, 2, 3, 4);

The same for the second scenario :

List<Customer> customers = new List<Customer>();
AddMultiple(customers,
         new Customer(),
         new Customer(),
         new Customer(), 
         new Customer());