XMLHttpRequest

<script type="text/javascript"><!--
        var request = null;

        function SelectedLetterChanged()
        {
            // Create an XMLHttpRequest object
            if (window.XMLHttpRequest)
            {
                request = new XMLHttpRequest();
            }
            else if (window.ActiveXObject)
            {
                request = new ActiveXObject("Microsoft.XMLHTTP");
            }

            // If the request is created successfully
            if (request)
            {
                // Retrieve the information for the new rows
                var letter = document.getElementById("DropDownList1").value;
                request.onreadystatechange = ReceiveRows;
                request.open("GET", "customers.aspx?letter=" + letter, true);
                request.send(null);
            }
        }

        function ReceiveRows(e)
        {
            if (request.readyState == 4 && request.status == 200)
            {
                // Delete the existing rows in the grid
                var grid = igtbl_getGridById("UltraWebGrid1");

                while(grid.Rows.length > 0)
                {
                    grid.Rows.getRow(0).deleteRow();
                }
            
                // Add new rows based on the information in the XML document
                var xml = request.responseXML;
                var dataRows = xml.getElementsByTagName("Customers");

                for (var x=0; x<dataRows.length; x++)
                {
                    // Create a new grid row
                    var gridRow = igtbl_addNew("UltraWebGrid1", 0);

                    // Copy the information from the data row into the grid row
                    var dataRow = dataRows[x];
                    for (var y=0; y<grid.Bands[0].Columns.length; y++)
                    {
                        var columnKey = grid.Bands[0].Columns[y].Key;
                        var data = dataRow.getElementsByTagName(columnKey)[0];

                        if (data)
                        {
                            gridRow.getCell(y).setValue(data.text);
                        }
                    }
                }
            }
        }
        --></script>

后台代码：

protected void Page_Load(object sender, System.EventArgs e)
        {
            // This page makes the contents of the dataset available as an XML file
            // that the javascript XmlHttpRequest object can download
            Response.ContentType = "text/xml";

            if (Request["letter"] != null) 
            {
                this.oleDbDataAdapter1.SelectCommand.CommandText = string.Format("SELECT * FROM Customers WHERE CustomerID LIKE \"{0}%\"", Request["letter"]);
                this.oleDbDataAdapter1.Fill(this.dataSet11);
            }

            this.dataSet11.WriteXml(Response.OutputStream);
            Response.End();
        }