Tuesday, October 13, 2009

Custom paging in Gridview With ObjectDataSource

Many times we use paging with GridView with AllowPaging = "True" and binding the GridView with some ObjectDataSource. It actually fetches all row from the database and depending on the no of records it fetched, it generates the Pager section of the page and according to the current page index, it shows the set of record.
This approach is good for when you have limited no of record in the database. But there are many situations where there is thousands of rows in the database and you have to display only 25 records(PageSize) out of that thousands of records. So it is not good practice to fetch all record through object datasource to display only 25 records.
Here we should use custom paging to fetch only the 25 rows starting from the startindex which is
CurrentPageIndex*PageSize (As Index is 0 Based).
Calculated automatically by objectdatasource.
Here is the change you have to do

  • Set EnablePaging="True" for ObjectDataSource

  • Set The SelectMethod Property

  • Set value for following Properties of ObjecDataSource StartRowIndexParameterName, SortParameterName, MaximumRowsParameterName
    These parameters needs to be present in the method attached for selecting the result for objectdatasource.

  • Set SelectCountMethod to the name of method returning the total no of rows.


Here is my ObjectDataSourceCode


<asp:objectdatasource id="objDS" runat="server" enablepaging="True" selectmethod="SearchResult" typename="PRP.BusinessLogic.TpilTblNsefaoscripmaster" startrowindexparametername="paramStartRowIndex" sortparametername="paramSortExpression" maximumrowsparametername="paramPageSize" selectcountmethod="GetNoOfRows">
<selectparameters>
<asp:parameter name="paramSymbol" type="String">
<asp:parameter direction="Output" name="paramTotalNoOfRows" type="Int32">
</asp:parameter>
</asp:parameter>
</selectparameters>
</asp:objectdatasource>


The SearchResult & GetNoOfRows Function


public DataTable SearchResult(string paramSymbol,
int paramStartRowIndex, int paramPageSize, string paramSortExpression, out int paramTotalNoOfRows)
{
TpilTblNsefaoscripmasterHelper.SearchResult(paramSymbol, paramStartRowIndex, paramStartRowIndex + paramPageSize, paramSortExpression, ref paramTotalNoOfRows);
this.totalNoOfRows = paramTotalNoOfRows;
}
int totalNoOfRows = 0;
public int GetNoOfRows(string paramSymbol,
int paramStartRowIndex, int paramPageSize, string paramSortExpression, out int paramTotalNoOfRows)
{
paramTotalNoOfRows = totalNoOfRows;
return totalNoOfRows;
}


The parameter list for both the functions are same but the second function retuns int no of rows. But i don't have used two function call for getting the total noofrows. Inside select function i have set the totalNoOfRows parameter which is accessed inside GetNoOfRows method to get the no of rows. This works as objectdatasource calls both the method on same object instance of the class and none of the methods and the class variable is static and the select methos is called first and then the row count method is called.
Now check the stored procedure used for this purpose


Create PROCEDURE [dbo].[USP_TPIL_tbl_NSEFAOScripSelectForSearch]
@Symbol varchar(50),
@StartIndex int = 0,
@EndIndex int =25,
@SortExpression varchar(50),
@TotalNoOfRows int OUTPUT
AS
SET NOCOUNT ON
Select * from
(
SELECT m.Instrument,m.Symbol,m.SymbolDescription,ExpiryDate,
Row_Number() OVER (Order By
CASE WHEN @SortExpression='EXPIRYDATE' OR @SortExpression='EXPIRYDATE ASC' THEN m.EXPIRYDATE END DESC,
CASE WHEN @SortExpression='EXPIRYDATE DESC' THEN m.EXPIRYDATE END ASC ,
CASE WHEN @SortExpression='SYMBOL' OR @SortExpression='SYMBOL ASC' THEN m.SYMBOL END DESC,
CASE WHEN @SortExpression='SYMBOL DESC' THEN m.SYMBOL END ASC
) as RowNumber
FROM
[dbo].[TPILl_NSEFAOScripMaster] m
WHERE
(m.[Symbol] LIKE @Symbol OR @Symbol = '')
)t
Where RowNumber>@StartIndex AND RowNumber<=@EndIndex --return SELECT @TotalNoOfRows = Count(*) FROM [dbo].[TPILl_NSEFAOScripMaster] m WHERE (m.[Symbol] LIKE @Symbol OR @Symbol = '')


As i am using Sql Server 2005, i used ROW_Number() function. The value of output parameter "TotalNoOfRows " is set to the variable "totalNoOfRows" inside "SearchResult" function.
To know about how to get Row Number in Sql Server 2000 please check the bottom of this link.

2 comments:

aisha said...

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H S Consultants said...

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