DataGrid Paging Problem

hoailing22 · June 28th, 2005, 05:13 AM

Hi, i have a datagrid to display the data retrieved from database using datareader. I set custom paging to false, it will give me the following error.

Server Error in '/e-library' Application.
--------------------------------------------------------------------------------

AllowCustomPaging must be true and VirtualItemCount must be set for a DataGrid with ID DgFaqs when AllowPaging is set to true and the selected datasource does not implement ICollection.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: AllowCustomPaging must be true and VirtualItemCount must be set for a DataGrid with ID DgFaqs when AllowPaging is set to true and the selected datasource does not implement ICollection.

Source Error:

Line 50: dr = cmd.ExecuteReader
Line 51: DgFaqs.DataSource = dr
Line 52: DgFaqs.DataBind()
Line 53: con.Close()
Line 54: End Sub

Source File: c:\inetpub\wwwroot\e-library\Help.aspx.vb Line: 52

Stack Trace:

[HttpException (0x80004005): AllowCustomPaging must be true and VirtualItemCount must be set for a DataGrid with ID DgFaqs when AllowPaging is set to true and the selected datasource does not implement ICollection.]
   System.Web.UI.WebControls.DataGrid.CreateControlHi erarchy(Boolean useDataSource) +2068
   System.Web.UI.WebControls.BaseDataList.OnDataBindi ng(EventArgs e) +49
   System.Web.UI.WebControls.BaseDataList.DataBind() +23
   e_library.Help.BindGrid() in c:\inetpub\wwwroot\e-library\Help.aspx.vb:52
   e_library.Help.Page_Load(Object sender, EventArgs e) in c:\inetpub\wwwroot\e-library\Help.aspx.vb:31
   System.Web.UI.Control.OnLoad(EventArgs e) +67
   System.Web.UI.Control.LoadRecursive() +35
   System.Web.UI.Page.ProcessRequestMain() +750

--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:1.1.4322.2032; ASP.NET Version:1.1.4322.2032

But if I set custom paging to true, the data is displayed, but I cant navigate through the records.

Below are my coding:

Code:

 Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not IsPostBack Then
            BindGrid()
        End If
        btnLogout.Attributes.Add("onclick", "return confirm('Are you sure you want to exit E-Library System?');")
    End Sub

    Private Sub BindGrid()
        Dim a As New Common
        Dim con As New SqlConnection
        con = a.GetConnect()

        DgFaqs.Visible = True
        Dim cmd As New SqlCommand
        Dim dr As SqlDataReader

        cmd.CommandText = "select * from FAQs"
        cmd.CommandType = CommandType.Text
        cmd.Connection = con
        con.Open()

        dr = cmd.ExecuteReader
        DgFaqs.DataSource = dr
        DgFaqs.DataBind()
        con.Close()
    End Sub

    Private Sub DgFaqs_PageIndexChanged(ByVal sender As System.Object, ByVal e As System.Web.UI.WebControls.DataGridPageChangedEventArgs)
        DgFaqs.CurrentPageIndex = e.NewPageIndex
        BindGrid()
    End Sub

Can somebody point out what is the problem behind this? Thanks a lot!

Irene

planoie · June 28th, 2005, 05:50 AM

Hi there Irene,

The problem here is with the DataReader class. Because of the way this class is built, it can't provide information on what lies ahead in the data. It provides a one-shot access to a current row of data because it's maintain a direct, live connection to the data source. When you call the Read() method it hits the data source again and gets the next row. Think of the DataReader as a data conveyor belt. You get the data as it comes but you never know how much there will be. The point of all this is that the DataReader (just as the error you are getting states) does not implement ICollection. It is not a collection.

If you were to use a DataTable (in a DataSet) you would not get this error. A DataTable has a collection of rows that implements ICollection. Think of a DataTable as a big barrel of data. When you get it you know how much is in it.

The DataGrid control expects to use the ICollection interface so you need to use something that implements that. In most cases this means changing your use of DataReader to DataSet/DataTable. This will mean you'll need to use a DataAdapter along with the Command and Connection classes.

-Peter

hoailing22 · June 28th, 2005, 06:17 AM

Hi Peter,

now I use dataset, & set custom paging to false. But even though the data is displayed,
the paging does not works. I set page size to 5 rows, even though I have 7 records,
it only allow me to view the first 5 records.

Is it I miss out something?

Irene

planoie · June 28th, 2005, 08:19 AM

The "DgFaqs_PageIndexChanged" method is missing " Handles DgFaqs.PageIndexChanged"

-Peter

naresh.net · June 28th, 2005, 10:39 PM

hi there,
u can write a stored procedure that counts the rows od the data in a table.
then use a function (say fun_countrows) in the coding part that returns the no. of rows of the data.
then use this function as VirtualItemCount=fun_countrows
this may solve the problem.

'''''''''stored procedure
ALTER PROCEDURE proc_name
    (
        @NumOfRow int = 0
    )
AS
    SET @NumOfRow = (select count(*) as NumOfRow from proc_name);

    RETURN @NumOfRow

barisergun · April 23rd, 2006, 03:15 AM

Hello

The DataReaders read one-way data As I undesrtand you dynamically bind your Oracle Database to your Datagird. Try to convert oracleDataReader to DataView. DataViews can be red 2 way and they are Compatible with AllowPaging=true

I have recently sent a Control to Asp.Net I think it is in the proccessing stage that Control converts OdbcDataReader to DataView below is the open code for you to give you an idea. You must apply the same logic to your Oracle Reader

Good Luck,

Baris ERGUN

www.thecoreopsis.com

public static DataView ConvertToDataView(OdbcDataReader setToCheck, string tableName)

{

DataTable dataReaderTable = new DataTable(tableName);

try

{

for(int h=0;h<setToCheck.FieldCount;h++)

{

DataColumn temp = new DataColumn(setToCheck.GetName(h),setToCheck.GetFie ldType(h));

dataReaderTable.Columns.Add(temp);

}

while(setToCheck.Read())

{

DataRow dr = dataReaderTable.NewRow();

for(int g=0;g<setToCheck.FieldCount;g++)

{

dr[g] = setToCheck.GetValue(setToCheck.GetOrdinal(setToChe ck.GetName(g)));

}

dataReaderTable.Rows.Add(dr);

}

return dataReaderTable.DefaultView;

}

catch

{

return null;

}

}