Linq Any() times out - asp.net

Question

I am trying to compare two data tables using Linq. Very simple tables, just one column but have about 44,000 rows. I use the following but when I trace it, when it gets to if (dr.Any()), it just sits there and next line, or exception, is never executed:
public static DataTable GetTableDiff(DataTable dt1, DataTable dt2)
{
DataTable dtDiff = new DataTable();
try
{
var dr = from r in dt1.AsEnumerable() where !dt2.AsEnumerable().Any(r2 => r["FacilityID"].ToString().Trim().ToLower() == r2["FacilityID"].ToString().Trim().ToLower()) select r;
if (dr.Any())
dtDiff = dr.CopyToDataTable();
}
catch (Exception ex)
{
}
return dtDiff;
}
I set max request length in web.config to make sure that is not an issue, but no change:
<system.web>
<compilation debug="true" targetFramework="4.5" />
<httpRuntime targetFramework="4.5" maxRequestLength="1048576" />
I don't think 44,000 rows is too big, is it?

Answer 1

Join tables O(N1+N2) instead of doing O(N1*N2) search (currently for each row in dt1 you are scanning all rows in dt2):
var diff = from r1 in dt1.AsEnumerable()
join r2 in dt2.AsEnumerable()
on r1.Field<string>("FacilityID").Trim().ToLower()
equals r2.Field<string>("FacilityID").Trim().ToLower() into g
where !g.Any() // get only rows which do not have joined rows from dt2
select r1;
With join you will also calculate each key (facility id) only once.
Another option is creating simple row comparer:
public class FacilityIdComparer : IEqualityComparer<DataRow>
{
public bool Equals(DataRow x, DataRow y) => GetFacilityID(x) == GetFacilityID(y);
public int GetHashCode(DataRow row) => GetFacilityID(row)?.GetHashCode() ?? 0;
private string GetFacilityID(DataRow row)
=> row.Field<string>("FacilityID")?.Trim().ToLower();
}
Then getting new rows is one liner with LINQ Except method:
var diff = dt2.AsEnumerable().Except(dt1.AsEnumerable(), new FacilityIdComparer());
and it will work for searching intersections as well

Answer 2

I would use a different, more leightweight, approach because you just take rows from one table and you want only those with a new FacilityId:
public static DataTable GetTableDiff(DataTable dtNew, DataTable dtOld)
{
DataTable dtDiff = dtNew.Clone(); // no data only columns and constraints
var oldFacilityIds = dtOld.AsEnumerable().Select(r => r.Field<string>("FacilityID").Trim());
var oldFacilityIDSet = new HashSet<string>(oldFacilityIds, StringComparer.CurrentCultureIgnoreCase);
var newRows = dtNew.AsEnumerable()
.Where(r => !oldFacilityIDSet.Contains(r.Field<string>("FacilityID").Trim()));
foreach (DataRow row in newRows)
dtDiff.ImportRow(row);
return dtDiff;
}