With that out of the way, my original problem did not disappear.

TEST 1:

SELECT CONVERT(INT, nsFramework.dbo.fncFormulaCalculation(5, 1, tYear, tMonth, 0))

FROM dbo.tblTallyTable_Periods

WHERE tYear = 2014

-----------

26746

23014

27048

26326

27356

25219

27667

27823

25650

28139

27386

26956

TEST 2: (fail)

CREATE TABLE #Temp (

Result INT)

INSERT INTO #Temp

SELECT CONVERT(INT, nsFramework.dbo.fncFormulaCalculation(5, 1, tYear, tMonth, 0))

FROM dbo.tblTallyTable_Periods

WHERE tYear = 2014

SELECT * FROM #Temp

DROP TABLE #Temp

(12 row(s) affected)

Result

-----------

0

0

0

0

0

0

0

0

0

0

0

0

(12 row(s) affected)

Now why would the exact same statement fails only because I am trying to insert the result into a temp table? I know it is the clr function that is returning the zeroes, because I set the result to 0 when an error is occured. So something changes when I try to write back to SQL and the clr function knows about the change. The question is what must I change in the clr for it to work the same with test 1 and test 2?