Applying Extension Methods to an Interface in C#

[ShervanN]

Hello,

Could you please write an example for applying extension methods to an interface in C#? Which allows me to call the extension method on all the classes that implement the interface.

Thank you in advance

[christiannagel]

Hi Shervan,

Page 75 shows an extension method that extends the string type.
On page 230 you can see an extension method for IEnumerable<TSource>:

public static IEnumerable<TSource> Where<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate> predicate)
{
    foreach (TSource item in source)
    {
        if (predicate(item))
            yield return item;
    }
}

With this, you can invoke the Where method on every object implementing IEnumerable<T>.

[ShervanN]

Great.