Alter proc [dbo].[InvoiceDisplayTest] (
    @InvoiceNumber nvarchar(50),
    @InvoiceDate datetime ,
    @InvoiceDate1 datetime, 
    @AccountNumber nvarchar(50),
    @TradingPartnerID nvarchar(50),
    @Page nvarchar(50),
    @rownum int OUTPUT)
AS
BEGIN
    SELECT *
    FROM (SELECT InvoiceID,DocumentNumber, convert(char(12),DocumentDate,112) AS DocumentDate,AccountNumber,Supplier,TradingPartnerID, 
          ROW_NUMBER()OVER(ORDER BY DocumentNumber ASC)AS rowno
          FROM InvoiceHeader
          WHERE
            (@InvoiceNumber = '' OR DocumentNumber = @InvoiceNumber)
            and (@AccountNumber = '' or AccountNumber = @AccountNumber)
            and (@TradingPartnerID = '' or TradingPartnerID = @TradingPartnerID)
            and (@InvoiceDate = '' or DocumentDate >= @InvoiceDate
            and DocumentDate <=@InvoiceDate1 or @InvoiceDate1 = '')
         )As qr
    WHERE
        rowno BETWEEN ((@Page - 1) * 20 + 1)
        AND (@Page * 20)

    SET @rownum = @@rowcount;

END

Alter proc [dbo].[InvoiceDisplayTest] (@InvoiceNumber nvarchar(50),@InvoiceDate datetime ,@InvoiceDate1 datetime, @AccountNumber nvarchar(50),@TradingPartnerID nvarchar(50),@Page nvarchar(50),@rownum int OUTPUT)
AS
BEGIN
SELECT * FROM (SELECT InvoiceID,DocumentNumber, convert(char(12),DocumentDate,112) AS DocumentDate,AccountNumber,Supplier,TradingPartnerID, 

ROW_NUMBER()OVER(ORDER BY DocumentNumber ASC)AS rowno,

COUNT(*) OVER() AS TotalRows

 FROM InvoiceHeader

WHERE (@InvoiceNumber = '' OR DocumentNumber = @InvoiceNumber)
and
(@AccountNumber = '' or AccountNumber = @AccountNumber)
and
(@TradingPartnerID = '' or TradingPartnerID = @TradingPartnerID)
and
(@InvoiceDate = '' or DocumentDate >= @InvoiceDate
and
DocumentDate <=@InvoiceDate1 or @InvoiceDate1 = '')
)As qr
WHERE rowno BETWEEN ((@Page - 1) * 20 + 1)
AND (@Page * 20)

END

We walk in the dark places no others will enter
We stand on the bridge and no one may pass