IDE proclaims I need an object reference for a field, method in class

</<pre lang="c#">
namespace API.Core.Da
{
	
	[ServiceContract]
	public interface IServers
	{
	 Opc.Server[] GetRemoteServers(string host);
        }


	[DataContract]
	public class Servers : MarshalByRefObject, IServers
	{


	// A
	// This method the IDE tooltip says that an object reference is required for the non static field, method, property GetRemoteServers 
	[OperationContract]
	public Opc.Server[] GetRemoteServers(string host)
	{
	  IDiscovery discovery = new OpcCom.ServerEnumerator();
 	  //Get all OPC DA servers of version 2.0 of machine "MyMachine"
 	  Opc.Server[] hostservers = discovery.GetAvailableServers(Specification.COM_DA_20, host, null);
	  return hostservers;
	}



		// A
		// This method the IDE tooltip says that an object reference is required for the non static field, method, property CreateServer 
		[OperationContract]
		public Opc.Da.Server CreateServer(Opc.URL url, System.Net.NetworkCredential credentials)
		{

			Opc.Da.Server client = null ;
			OpcCom.Factory fact = new OpcCom.Factory();
			client = new Opc.Da.Server(fact, url );
			return client;
			
		}

		// B
		// This method the IDE tooltip does not say it requires any object reference it just shows the tooltip that a good method should.
		[OperationContract]
		public Opc.Da.Server CreateServer(string OpcUrl, OpcCom.Factory factory, System.Net.NetworkCredential Credential)
		{
	 
			Opc.URL Url = new Opc.URL(OpcUrl);
			Opc.Da.Server client = new Opc.Da.Server(factory, null );
			client.Connect(Url, new Opc.ConnectData(Credential));
			return client;
			
		}


	}

}