Retrieve CRM Entity's Picklist using MetadataService

This method returns a NameValueCollection of picklist items. CrmHelper is similar to the SDK utility sample.

public NameValueCollection GetAgencyRelationshipTypePicklist()
{
    CrmHelper helper = new CrmHelper();

    NameValueCollection picklist = new NameValueCollection();

    RetrieveAttributeRequest attribReq = new RetrieveAttributeRequest();
    attribReq.EntityLogicalName = "new_agencycontact";
    attribReq.LogicalName = "new_agencycontacttype";
    attribReq.RetrieveAsIfPublished = true;

    MetadataService service = helper.GetMetadataService(); 

    RetrieveAttributeResponse attribResp = service.Execute(attribReq) as RetrieveAttributeResponse;

    PicklistAttributeMetadata listData = attribResp.AttributeMetadata as PicklistAttributeMetadata;

    foreach (Option item in listData.Options)
    {
        picklist.Add(item.Value.formattedvalue, item.Label.UserLocLabel.Label);
    }

    return picklist;
}