add THREE table A&B&C coloums

Hi,
You can try this way also
DECLARE    @tbl_1 AS TABLE (sno INT IDENTITY(1,1),item NVARCHAR(100),amount money);
DECLARE    @tbl_2 AS TABLE  (sno INT IDENTITY(1,1),item NVARCHAR(100),amount money);
DECLARE    @tbl_3 AS TABLE (sno INT IDENTITY(1,1),item NVARCHAR(100),amount MONEY);


INSERT INTO @tbl_1 VALUES ('asdf',545.00);

INSERT INTO @tbl_2 VALUES ('dfgh',876);


WITH cte (item,amount ) AS
(
SELECT item,amount FROM @tbl_1 AS t
UNION
SELECT item,amount FROM  @tbl_2 AS t2
UNION
SELECT item,amount FROM @tbl_3 AS t3

)

SELECT item,amount FROM (

SELECT item,amount FROM     cte
UNION ALL
SELECT
'total' ,SUM(amount)
FROM  cte

) AS result

if u are going to do this in c# then that will very difficult process. it can done in database in very simple way.

CREATE   TABLE #tbl_1 (sno INT IDENTITY(1,1),name NVARCHAR(100),id INT)
CREATE   TABLE #tbl_2 (sno INT IDENTITY(1,1),name NVARCHAR(100),id INT)
CREATE   TABLE #tbl_3 (sno INT IDENTITY(1,1),name NVARCHAR(100),id INT)


INSERT INTO #tbl_1 VALUES ('kiran','9876')
INSERT INTO #tbl_1 VALUES ('praveen','7654')


INSERT INTO #tbl_2 VALUES ('raju','245')
INSERT INTO #tbl_2 VALUES ('vamshi','386')
---------------------------------------------------------
DECLARE @Results TABLE ( name NVARCHAR(100),id INT)


INSERT INTO @Results
SELECT *
FROM ( 
SELECT name,id FROM #tbl_1
UNION ALL
SELECT name,id FROM #tbl_2
UNION ALL
SELECT name,id FROM #tbl_3
) temp


SELECT * FROM  @Results
UNION ALL
SELECT
'total' ,SUM(id)
FROM  @Results


DROP TABLE #tbl_1
DROP TABLE #tbl_2
DROP TABLE #tbl_3