but give me error that invalid object name #temp2 - sql-server

Question

Alter procedure spMRI_TAG_try
#DocNum int
as
declare #cnt int
declare #count int
declare #cardname nvarchar(100)
declare #Docdate datetime
declare #itemCode nvarchar(50)
declare #Dscription nvarchar(100)
declare #Quantity numeric(19,6)
declare #ManBtchNum char(1)
declare #SalPackUn numeric(19,6)
declare #ExpDate datetime
begin
set #cnt = 1
select #Count = pdn1.Quantity/OITM.SalPackUn from pdn1 inner join OITM on pdn1.ItemCode=OITM.ItemCode
while #cnt <= #count
insert into #temp2 values(#cardname,#DocDate,#itemcode,#Dscription,#Quantity,#ManBtchNum,#SalPackUn,#ExpDate)
select #cardname = a.CardName,#DocDate=a.DocDate,#itemcode=b.ItemCode,#Dscription=b.Dscription,#Quantity=b.Quantity,#ManBtchNum=c.ManBtchNum,#SalPackUn=c.SalPackUn,#ExpDate=d.ExpDate
from OPDN a inner join PDN1 b on a.DocEntry = b.DocEntry inner join OITM c on c.ItemCode = b.ItemCode inner join OBTN d on c.ItemCode = d.ItemCode and a.DocNum=#DocNum and d.ExpDate is not null
set #cnt=#cnt+1
end
select * from #temp2
but gives me an invalid object name #temp2 error.

Answer 1

Create temp table before your while loop:
create table #temp2 (Cardname ...)
while #cnt <= #count
insert into #temp2 values(#cardname,#DocDate,#itemcode,#Dscription,#Quantity,#ManBtchNum,#SalPackUn,#ExpDate)
select #cardname = a.CardName,#DocDate=a.DocDate,#itemcode=b.ItemCode,#Dscription=b.Dscription,#Quantity=b.Quantity,#ManBtchNum=c.ManBtchNum,#SalPackUn=c.SalPackUn,#ExpDate=d.ExpDate
Two points here:
Not sure why you are using looping - Try set based approaches. You can solve most of the problems in set based queries
You can create temp tables using select * into #temp2... Check for that syntax in msdn

Answer 2

To be honest your SP is a one big messed up code :)
I suggest you to rewrite it like this:
ALTER PROCEDURE spMRI_TAG_try
#DocNum int
AS
--Drop table if it exists
IF OBJECT_ID(N'#temp2') IS NOT NULL DROP TABLE #temp2
--create table
CREATE TABLE #temp2 (
cardname nvarchar(100),
Docdate datetime,
itemCode nvarchar(50),
Dscription nvarchar(100),
Quantity numeric(19,6),
ManBtchNum char(1),
SalPackUn numeric(19,6),
ExpDate datetime
)
--Make the insertion
INSERT INTO #temp2
SELECT a.CardName,
a.DocDate,
b.ItemCode,
b.Dscription,
b.Quantity,
c.ManBtchNum,
c.SalPackUn,
d.ExpDate
FROM OPDN a
INNER JOIN PDN1 b
ON a.DocEntry = b.DocEntry
INNER JOIN OITM c
ON c.ItemCode = b.ItemCode
INNER JOIN OBTN d
ON c.ItemCode = d.ItemCode and a.DocNum=#DocNum and d.ExpDate is not null
--output
SELECT *
FROM #temp2
No need a while loop (I can not even understand how you will switch through the rows, in your solution it will write the same row the '#count' times), you can write all data directly in temp table.
You get error because of there is no #temp2 table on the moment you are trying to insert, also there is no checking if the table already exists.
As was noted in answer by Kannan Kandasamy, the one more way is to use SELECT * INTO #temp2, it can be achieved this way:
ALTER PROCEDURE spMRI_TAG_try
#DocNum int
AS
IF OBJECT_ID(N'#temp2') IS NOT NULL DROP TABLE #temp2
SELECT a.CardName,
a.DocDate,
b.ItemCode,
b.Dscription,
b.Quantity,
c.ManBtchNum,
c.SalPackUn,
d.ExpDate
INTO #temp2
FROM OPDN a
INNER JOIN PDN1 b
ON a.DocEntry = b.DocEntry
INNER JOIN OITM c
ON c.ItemCode = b.ItemCode
INNER JOIN OBTN d
ON c.ItemCode = d.ItemCode and a.DocNum=#DocNum and d.ExpDate is not null
SELECT *
FROM #temp2