An improvement of the code in the article "Walkthrough: creating paged data access using web form pages" in MSDN

If you install it MSDN, Learning to use .NET Make a website , You may encounter such a sample document ：

Visual Basic and Visual C# Concept

rehearse ： Use Web Form pages create paged data access

ms-help://MS.VSCC.2003/MS.MSDNQTR.2003FEB.2052/vbcon/html/vbwlkwalkthroughdisplayingdatainlistboxesonwebformspage.htm

This article describes how to create a data list with custom paging , The feature is that only the corresponding number of pieces of data are extracted from the database each time , This method is very good for the list display of large data tables , It is better than another scheme that takes out all the data at once and then caches the pages .

When I adopted this scheme, I found several small BUG, as follows ：

1. stay “ Go to the next page ” In the program code of ,

   private void btnNext_Click(object sender, System.EventArgs e)
   {
      // Get the page number of the page most recently displayed
      CurrentPage = (int)(ViewState["CurrentPage"]);
      CurrentPage++;
      // Gets the id on current page
      string lastid = DataGrid1.Items[9].Cells[0].Text;
      cmdNext.Parameters["@customerid"].Value = lastid;
      FillGrid(cmdNext);
   }
   The scarlet letter should read “string lastid = DataGrid1.Items[DataGrid1.PageSize-1].Cells[0].Text;”, Otherwise, when the number of （PageSize） Not the default 10 Stripe time , May cause errors .

2. In addition to “ Show data in Grid ” In this part , You will see that some codes judge when the number of entries taken on this page is less than PageSize when , That is, when it is regarded as the last page of the data table , Set up “ The next page ” Button failure , You should also add the judgment that the current page is 0 Or less than 0 when , That is, when it is regarded as the first page of the data sheet , Set up “ The previous page ” Button failure code , as follows ：

      if (DataGrid1.Items.Count < DataGrid1.PageSize)
      {
       btnNext.Enabled = false;
      }
      if (CurrentPage <= 0)
      {
       btnPrevious.Enabled = false;
      }
   

3. Steps in 2 At the same time , stay btnNext_Click This sentence should also be added to the method “this.btnPrevious.Enabled = true;”, So that after page change “ The previous page ” Button activated first , Then follow the steps 2 To judge whether the setting button is invalid .
4. Add ： A new problem has just been found in the inspection , When the number of entries on the last page is just the number of entries on the page ,“ The next page ” The button is still active , Click to make an error , Because there is no corresponding record to display . Therefore, the following supplementary amendments are made ：（ Pay attention to the red marking ）

      if(dr.HasRows==true)
      {
       DataGrid1.DataSource = dr;
       DataGrid1.DataBind();
       dr.Close();
       sqlConnection1.Close();
       ViewState["CurrentPage"] = CurrentPage;
       ViewState[CurrentPage.ToString()] = DataGrid1.Items[0].Cells[0].Text;
       if (DataGrid1.Items.Count < DataGrid1.PageSize)
       {
        btnNext.Enabled = false;
       }
       if (CurrentPage <= 0)
       {
        btnPrevious.Enabled = false;
       }
      }
      else
      {
       btnNext.Enabled = false;
      }

thus , After my test, such a paging list is more perfect , You can adapt to different page numbers .