Having code as below, getting a compile error - "... does not implement interface member 'System.Collections.IEnumerable.GetEnumerator()'".
How to implement the non-generic version of GetEnumerator?
public class Giraffe { } public class Pigeon { } public class Sample : IEnumerable<Giraffe>, IEnumerable<Pigeon> { IEnumerator<Giraffe> IEnumerable<Giraffe>.GetEnumerator() { return null; } IEnumerator<Pigeon> IEnumerable<Pigeon>.GetEnumerator() { return null; } } Try:
public class Pets :IEnumerable, IEnumerable<Giraffe>, IEnumerable<Pigeon> { IEnumerator<Giraffe> IEnumerable<Giraffe>.GetEnumerator() { return null; } IEnumerator<Pigeon> IEnumerable<Pigeon>.GetEnumerator() { return null; } public IEnumerator GetEnumerator() { throw new NotImplementedException(); } } 
using System.Collection to your using list. Its not defined in the System.Collection.Generics namespace.
NotSupportedException in this case (since by design the method will not be implemented).if I understand your problem correctly, here is a sample how you can implement non-generic Enumerator in your class
public class Sample : IEnumerable<Giraffe>, IEnumerable<Pigeon> { IEnumerator<Giraffe> IEnumerable<Giraffe>.GetEnumerator() { return null; } IEnumerator<Pigeon> IEnumerable<Pigeon>.GetEnumerator() { return null; } IEnumerator IEnumerable.GetEnumerator() { return null; //your logic for the enumerator } } since the generic IEnumerable<T> inherits non-generic IEnumerable so implementing IEnumerable.GetEnumerator would define an implementation for the same.
you may additionally declare the class as public class Sample : IEnumerable, IEnumerable<Giraffe>, IEnumerable<Pigeon> for more clarity
example
public class Sample : IEnumerable, IEnumerable<Giraffe>, IEnumerable<Pigeon> { IEnumerator<Giraffe> IEnumerable<Giraffe>.GetEnumerator() { return null; } IEnumerator<Pigeon> IEnumerable<Pigeon>.GetEnumerator() { return null; } IEnumerator IEnumerable.GetEnumerator() { return null; //your logic for the enumerator } } 