/// <summary>
        /// Executes the specified workflow.
        /// </summary>
        /// <param name="rockContext">The rock context.</param>
        /// <param name="action">The action.</param>
        /// <param name="entity">The entity.</param>
        /// <param name="errorMessages">The error messages.</param>
        /// <returns></returns>
        public override bool Execute( RockContext rockContext, WorkflowAction action, Object entity, out List<string> errorMessages )
        {
            errorMessages = new List<string>();

            Guid? groupGuid = null;
            string filterValue = string.Empty;
            string filterKey = string.Empty;

            // get the group attribute
            groupGuid = GetAttributeValue( action, "SelectionGroup" ).AsGuid();

            if ( !groupGuid.HasValue )
            {
                errorMessages.Add("The selection group could not be found!");
            }

            // get filter key
            filterKey = GetAttributeValue( action, "GroupMemberAttributeKey" );

            // get the filter value
            filterValue = GetAttributeValue( action, "FilterValue" );
            Guid? filterValueGuid = filterValue.AsGuidOrNull();
            if ( filterValueGuid.HasValue )
            {
                filterValue = action.GetWorklowAttributeValue( filterValueGuid.Value );
            }
            else
            {
                filterValue = filterValue.ResolveMergeFields( GetMergeFields( action ) );
            }

            // get group members
            var qry = new GroupMemberService( rockContext ).Queryable().AsNoTracking()
                                    .Where( g => g.Group.Guid == groupGuid );

            if (!string.IsNullOrWhiteSpace(filterKey)){
                qry = qry.WhereAttributeValue( rockContext, filterKey, filterValue );
            }

            var groupMembers = qry.Select( g => new {
                                        g.Person.NickName,
                                        g.Person.LastName,
                                        g.Person.SuffixValueId,
                                        PrimaryAliasGuid = g.Person.Aliases.FirstOrDefault().Guid } )
                                   .ToList();

            if ( groupMembers.Count() > 0 )
            {
                // get random group member from options
                Random rnd = new Random();
                int r = rnd.Next( groupMembers.Count );

                var selectedGroupMember = groupMembers[r];

                // set value
                Guid selectPersonGuid = GetAttributeValue( action, "SelectedPerson" ).AsGuid();
                if ( !selectPersonGuid.IsEmpty() )
                {
                    var selectedPersonAttribute = AttributeCache.Read( selectPersonGuid, rockContext );
                    if ( selectedPersonAttribute != null )
                    {
                        // If this is a person type attribute
                        if ( selectedPersonAttribute.FieldTypeId == FieldTypeCache.Read( Rock.SystemGuid.FieldType.PERSON.AsGuid(), rockContext ).Id )
                        {
                            SetWorkflowAttributeValue( action, selectPersonGuid, selectedGroupMember.PrimaryAliasGuid.ToString() );
                        }
                        else if ( selectedPersonAttribute.FieldTypeId == FieldTypeCache.Read( Rock.SystemGuid.FieldType.TEXT.AsGuid(), rockContext ).Id )
                        {
                            SetWorkflowAttributeValue( action, selectPersonGuid, Person.FormatFullName(selectedGroupMember.NickName, selectedGroupMember.LastName, selectedGroupMember.SuffixValueId)  );
                        }
                    }
                }
            }
            else
            {
                errorMessages.Add( "No group member for the selected campus could be found." );
            }

            errorMessages.ForEach( m => action.AddLogEntry( m, true ) );

            return true;
        }