Compare 2 datatables with 3 columns and get unmatched records

Hi, how can I compare 2 datatables with multiple columns to get unmatched records? Previously I was using for each with a linq query but it takes too long for 100k over rows as there are many other validations as well.
Is there a way this can return a count with linq query?

For example:
DT1:
Col1 Country Col3 FirstName Col4 LastName

DT2:
Country FirstName Col3 LastName

I would like to check if the DT1 Country, FirstName and LastName matches the row in DT2.

Previous linq query in for each for DT1:
(DT2.Select("[Country] = ‘"+row.item(“Country”).ToString+"’ And [FirstName] = ‘"+row.Item(“FirstName”).ToString+"’ And [LastName] = ‘"+row.Item(“LastName”).ToString+"’")).Length > 0

Have a try on following:
Variables:

configure the Columnnames which are to check

Assign Activity:
grafik

LINQ:

When interrested on dtLeft rows which have a match in dtRight

(From d1 In dtLeft.AsEnumerable
Let arrCHK = arrLCols.Select(Function (x) d1(x)).toArray
Where dtRight.AsEnumerable.Any(Function (d2) arrRCols.Select(Function (y) d2(y)).SequenceEqual(arrCHK))
Select r=d1).CopyToDataTable

When interrested on dtLeft rows which have a NO match in dtRight

(From d1 In dtLeft.AsEnumerable
Let arrCHK = arrLCols.Select(Function (x) d1(x)).toArray
Where NOT dtRight.AsEnumerable.Any(Function (d2) arrRCols.Select(Function (y) d2(y)).SequenceEqual(arrCHK))
Select r=d1).CopyToDataTable

When empty results are to expect, have a look here:
:ambulance: :sos: [FirstAid] Handling of The source contains no DataRows exception - News / Tutorials - UiPath Community Forum

Kindly note: the datatable.Select method is something else as the LINQ Operator Select

[HowTo] LINQ (VB.Net) Learning Catalogue - Help / Something Else - UiPath Community Forum