how to improve nested linq query

[miss786]

I would like to be able to call string tag1 & tag2 with multiple values, such as Api/test?tag1=123,456,789&tag2=987,654 However, the below contain function only allows me to call 45 values for each tag1 & tag2, anything more than 45 string values used to search tag1 & tag2, the code throws a nested query error: "$id":"1","Message":"An error has occurred.","ExceptionMessage":"Some part of your SQL statement is nested too deeply. Rewrite the query or break it up into smaller queries. I tried adding toList() to my tag1 method, but I keep getting syntax error: Cannot implicitly convert type 'System.Collections.Generic.List' to 'System.Linq.IQueryable'. An explicit conversion exists (are you missing a cast?) any further advice, would be very much appreciated. Thank you.

IQueryable Data = null;

            if (!string.IsNullOrEmpty(query.tag2))
            {                  
                var ids = query.tag2.Split(',');

                var dataMatchingTags = db.database\_BCs.Where(c => ids.Contains(c.TAG2));

                if (Data == null)
                    Data = dataMatchingTags;
                else
                    Data = Data.Union(dataMatchingTags);
            }

            if (!string.IsNullOrEmpty(query.tag1))
            {
                var ids = query.tag1.Split(',');

                var dataMatchingTags = db.database\_BCs.Where(c => ids.Contains(c.TAG1));

                if (Data == null)
                    Data = dataMatchingTags;
                else
                    **Data = Data.Union(dataMatchingTags).ToList();**
            }

            if (Data == null) // If no tags is being queried, apply filters to the whole set of products
                Data = db.database\_BCs;

            if (query.dl\_type != null)
            {
                Data = Data.Where(c => c.Type == query.dl\_type);
            }
			
	  **var data = Data.ToList();**

            if (!data.Any())
            {
                var message = string.Format("No data found");
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, message);
            }