Microsoft KB Archive/320626

= HOW TO: Perform Paging with the DataGrid Windows Control by Using Visual J# .NET =

Article ID: 320626

Article Last Modified on 5/13/2007

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APPLIES TO


 * Microsoft Visual J# .NET 2003 Standard Edition
 * Microsoft Visual J# .NET 2003 Standard Edition

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This article was previously published under Q320626



For a Microsoft Visual Basic .NET version of this article, see 305271.

For a Microsoft Visual C# .NET version of this article, see 307710.

IN THIS TASK
SUMMARY
 * Requirements
 * Steps to Add Paging to a DataGrid Windows Control
 * Troubleshooting

REFERENCES



SUMMARY
The DataGrid Web control has built-in Automatic or Custom Paging functionalities; however, the DataGrid Windows control lacks these features. This article demonstrates how to create a simple paging mechanism for the DataGrid Windows control.

The code samples in this article use DataSet objects. In ADO.NET, DataSet objects are filled in a single operation and reside in memory all of the time. If you are working with a large DataSet, this article describes how to display the data in chunks or pages programmatically.

This sample uses the Customers table from the Microsoft SQL Server Northwind database as the database backend. If you connect to any other database or to a different table, make sure that you update the code accordingly.

This technique has some limitations. See the Troubleshooting section for more information.

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Requirements
The following list outlines the recommended hardware, software, network infrastructure, and service packs that are required:
 * Microsoft Windows 2000 Professional, Microsoft Windows 2000 Server, Microsoft Windows 2000 Advanced Server, Microsoft Windows NT 4.0 Server or later
 * Microsoft Visual Studio .NET
 * Microsoft Visual J# .NET Beta 2
 * Microsoft SQL Server 7.0 or later

This article assumes that you are familiar with the following topics:
 * Visual J# .NET
 * ADO.NET fundamentals and syntax

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Steps to Add Paging to a DataGrid Windows Control
When you page a DataGrid, you display data in page-size &quot;chunks,&quot; that is, one page of records at a time. The sample code to follow copies the DataRow objects for each page from the DataSet in memory to a temporary table. The temporary table is then bound to the DataGrid control.  Open a new Visual J# .NET Windows Application project. Add DataGrid control, and then set its ReadOnly property to True. Place the following additional controls on Form1, and set their properties as follows:

 In the Toolbox, click the Data tab. Double-click the SqlDataAdapter. Follow the instructions in the wizard. Right-click the SqlDataAdapter.</li> Click to select Generate Data Set.</li> Follow the instructions in the wizard.</li> Open the properties for the SqlConnection. If you do not see the logon password after the user ID, type it.</li>  Paste the following code in the top of the Form1 Code window. Make sure that each namespace is referenced just one time. By default, System and System.Data may already be referenced. import System.*; </li>  Paste the following code at the top of public class Form1 to declare form-level variables for Form1: DataTable dtSource; int PageCount; int maxRec; int pageSize; int currentPage; int recNo; </li>  Paste the following code in the constructor for the form: // Standard Error Handling try {                 // Get Data dtSource = dataSet11.get_Tables .get_Item(&quot;customers&quot;); // Fill the DataSet sqlDataAdapter1.Fill (dataSet11, &quot;customers&quot;); }           catch (Exception error) {                 // Display Error MessageBox.Show (&quot;Constructor failed with error: &quot; + error); }                   </li>  Paste the following code immediately after the static void Main method so that this code is form-level in scope: // Get Data private void LoadPage {

// Local Declaration int loop, start, stop, rows; DataTable dtTemp;

// Standard Error Handling try {

// Initialize rows = dtSource.get_Rows .get_Count ; dtTemp = dtSource.Clone ;

// Error Checking if (rows < 1) {                       MessageBox.Show (&quot;No Data to Show&quot;, &quot;Empty Table&quot;); return; }

// Set Loop Values if (currentPage == PageCount) stop = maxRec; else stop = pageSize * currentPage; start = recNo;

// Transfer Data to Temporary Table for (loop = start; loop < stop; loop ++) {                       dtTemp.ImportRow (dtSource.get_Rows .get_Item(loop)); recNo ++; }

// Show Data dataGrid1.set_DataSource (dtTemp); DisplayPageInfo ;

}           catch (Exception error) {                 MessageBox.Show (&quot;LoadPage failed with error: &quot; + error); }

}

// Output Data private void DisplayPageInfo {           txtDisplayPageNo.set_Text (&quot;Page &quot; + currentPage + &quot; / &quot; + PageCount); }

// Notify to Fill Data Grid private boolean CheckFillButton {

// Check if the user clicks the &quot;Fill Grid&quot; button. if (pageSize == 0) {                 MessageBox.Show(&quot;Set the Page Size, and then click the Fill Grid button!&quot;); return false; }           else {return true;}

}                   </li>  Double-click the Fill Grid button to open the code window for btnFillGrid. Paste the following code in the btnFillGrid_Click event procedure: // Set the start and max records. pageSize = Convert.ToInt32(txtPageSize.get_Text ); maxRec = dtSource.get_Rows .get_Count ; PageCount = maxRec / pageSize;

// Adjust the page number if the last page contains a partial // page if ((maxRec % pageSize) > 0) PageCount ++;

// Initial seeings currentPage = 1; recNo = 0;

// Display the content of the current page. LoadPage; </li>  Double-click the First Page button to open the code window for btnFirstPage. Paste the following code in the btnFirstPage_Click event procedure: // Verify Data if (CheckFillButton == false) return;

//Check if you are already at the first page. if (currentPage == 1) {                 MessageBox.Show(&quot;You are at the First Page!&quot;); return; }

// Reset to First Page currentPage = 1; recNo = 0; LoadPage; </li>  Double-click the Next Page button to open the code window for btnNextPage. Paste the following code in the btnNextPage_Click event procedure: // If the user did not click the &quot;Fill Grid&quot; button, then // return if (CheckFillButton == false) return;

// Check if the user clicks the &quot;Fill Grid&quot; button. if (pageSize == 0) {                 MessageBox.Show(&quot;Set the Page Size, and then click the Fill Grid button!&quot;); return; }           // Check if you are already at the last page. currentPage ++; if (currentPage > PageCount) {                 currentPage = PageCount; if (recNo == maxRec) {                       MessageBox.Show(&quot;You are at the Last Page!&quot;); return; }

}           LoadPage; </li>  Double-click the Previous Page button to open the code window for btnPreviousPage. Paste the following code in the btnPreviousPage_Click event procedure: // Notify User if (CheckFillButton == false) return;

// Set Record Count if (currentPage == PageCount) recNo = pageSize * (currentPage - 2); //Check if you are already at the first page. currentPage --; if (currentPage < 1) {                 MessageBox.Show(&quot;You are at the First Page!&quot;); currentPage = 1; return; }           else {recNo = pageSize * (currentPage - 1);} LoadPage; </li>  Double-click the Last Page button to open the code window for btnLastPage. Paste the following code in the btnLastPage_Click event procedure: // Notify User if (CheckFillButton == false) return; //Check if you are already at the last page. if (recNo == maxRec) {                 MessageBox.Show(&quot;You are at the Last Page!&quot;); return; }           // Set Tracking currentPage = PageCount; recNo = pageSize * (currentPage - 1); LoadPage; </li> Press the F5 key to build and run the project.</li> By default, the Page Size is set to 5 records. You can change this in the text box.</li> Click Fill Grid. Notice that the DataGrid is filled with 5 records.</li> <li>Click First Page, Next Page, Previous Page, and Last Page to view these pages.</li></ol>

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Troubleshooting

 * This technique only works for read-only DataGrid controls. When you import a row to a temporary DataTable object, you make a copy. Therefore, changes that you make are not saved to the main table.
 * This technique does not work (and neither does a collection or an array) if you want the user to be able to locate child records through a DataRelation object or if you have records that are linked in a parent-child relation and that appear on the form at the same time.

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