Save values on Postback - asp.net

Question

I have been doing custom paging for a datagrid where i retrieve only 10 values per page. So, I started doing it this way :
<asp:GridView ID="grid1" runat="server"
> </asp:GridView>
<asp:Button ID="Btn_Previous" CommandName="Previous" runat="server"
OnCommand="ChangePage" Text="Previous" />
<asp:Button ID="Btn_Next" runat="server" CommandName="Next" OnCommand="ChangePage"
Text="Next" />
<asp:Label ID="lblTotalPages" runat="server"></asp:Label>
<asp:Label ID="lblCurrentPage" runat="server"></asp:Label>
protected int currentPageNumber = 1;
protected const int PAGE_SIZE = 10;
protected int startrowindex=1;
protected void Page_Load(object sender, EventArgs e)
{
BindData();
}
private void BindData()
{
using (SqlConnection conn = new SqlConnection("Data Source=NISHANTH-PC\\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"))
{
conn.Open();
SqlCommand myCommand = new SqlCommand("GetProductsPaged",
conn);
myCommand.CommandType = CommandType.StoredProcedure;
myCommand.Parameters.AddWithValue("#startRow",
startrowindex);
myCommand.Parameters.AddWithValue("#maximumRows", PAGE_SIZE);
myCommand.Parameters.Add("#totalRows", SqlDbType.Int, 4);
myCommand.Parameters["#totalRows"].Direction = ParameterDirection.Output;
SqlDataAdapter ad = new SqlDataAdapter(myCommand);
DataSet ds = new DataSet();
ad.Fill(ds);
grid1.DataSource = ds;
grid1.DataBind();
double totalRows = (int)myCommand.Parameters["#totalRows"].Value;
lblTotalPages.Text = CalculateTotalPages(totalRows).ToString();
lblCurrentPage.Text = currentPageNumber.ToString();
if (currentPageNumber == 1)
{
Btn_Previous.Enabled = false;
if (Int32.Parse(lblTotalPages.Text) > 0)
{
Btn_Next.Enabled = true;
}
else
Btn_Next.Enabled = false;
}
else
{
Btn_Previous.Enabled = true;
if (currentPageNumber == Int32.Parse(lblTotalPages.Text))
Btn_Next.Enabled = false;
else Btn_Next.Enabled = true;
}
conn.Close();
}
}
private int CalculateTotalPages(double totalRows)
{
int totalPages = (int)Math.Ceiling(totalRows / PAGE_SIZE);
return totalPages;
}
protected void ChangePage(object sender, CommandEventArgs e)
{
switch (e.CommandName)
{
case "Previous":
currentPageNumber = currentPageNumber - 1;
startrowindex = startrowindex - 10;
break;
case "Next":
currentPageNumber = currentPageNumber + 1;
startrowindex = startrowindex + 10;
break;
}
BindData();
}
Basically, my problem has been that the grid works fine when the page loads. Then, since previous is hidden, when i click next it goes to second page and retrieves values perfectly. But when i click either on next or previous now, it goes all wrong. The reason i think is that, when I come back the currentpagenumber value at top is again becoming 1and startroeindex also becomes 1. Can u please let me know the way i can handle this?

Answer 1

I don't know your aspx page, but you need a way to send the previous page number. Otherwise, your script doesn't know what next means except 1+1. How do you change pages? Hyperlinks? If so, send the last page in a form field or query string.

Answer 2

first thing is that you are loading BindData on each and every post back, you must only call it on first time load.
Second thing, you are storing the in label, lblCurrentPage.Text = currentPageNumber.ToString(); So why dont you utilize the same and store it again on page_load event.
I have here provided the page_load event try this.
protected void Page_Load(object sender, EventArgs e)
{
currentPageNumber = Convert.ToInt32(lblCurrentPage.Text);
if(!IsPostback)
{
BindData();
}
}
please add default value for lblCurrentPage.Text to 1.