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First time working with UpdatePanels in .NET.
I have an updatepanel with a trigger pointed to an event on a FormView control. The UpdatePanel holds a ListView with related data from a separate database.
When the UpdatePanel refreshes, it needs values from the FormView control so that on the server it can use them to query the database.
For the life if me, I can't figure out how to get those values. The event I'm triggering from has them, but I want the updatepanel to refresh asynchronously. How do I pass values to the load event on the panel?
Googled this ad nauseum and can't seem to get to an answer here. A link or an explanation would be immensely helpful..
Jeff
718
Using ajax, the user can post data to the backend server without submitting the page or reloading the browser page. Creating an AJAX example application with a servlet is very simple.
Ajax makes use of the XMLHttpRequest object to communicate with servers. Using ajax, the user can post data to the backend server without submitting the page or reloading the browser page. Creating an AJAX example application with a servlet is very simple.
As you see the above code, it always return “Hello” because the ajax call is always generate another thread to run, not wait for it to return value so what is the correct way to do this?
Servlet class returns a JSON array as response upon invoking through Ajax call. Note that to create JSON objects, we need to add a dependency jar to the classpath or lib of our dynamic web project. In this example, we are using the org.json dependency jar.
make a javascript function that will collect the pieces of form data, and then sends that data to an ASHX handler. the ASHX handler will do some work, and can reply with a response.
This is an example I made that calls a database to populate a grid using AJAX calls. There are better libraries for doing AJAX (prototype, ExtJS, etc), but this is the raw deal. (I know this can be refactored to be even cleaner, but you can get the idea well enough)
Works like this...
The html will look like this...
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<script type="text/javascript" src="AjaxHelper.js"></script>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="txtSearchValue" runat="server"></asp:TextBox>
<input id="btnSearch" type="button" value="Search by partial full name" onclick="doSearch()"/>
<igtbl:ultrawebgrid id="uwgUsers" runat="server"
//infragistics grid crap
</igtbl:ultrawebgrid>--%>
</div>
</form>
</body>
</html>
The script that fires on click will look like this...
//this is tied to the button click. It takes care of input cleanup and calling the AJAX method
function doSearch(){
var eleVal;
var eleBtn;
eleVal = document.getElementById('txtSearchValue').value;
eleBtn = document.getElementById('btnSearch');
eleVal = trim(eleVal);
if (eleVal.length > 0) {
eleBtn.value = 'Searching...';
eleBtn.disabled = true;
refreshGridData(eleVal);
}
else {
alert("Please enter a value to search with. Unabated searches are not permitted.");
}
}
//This is the function that will go out and get the data and call load the Grid on AJAX call
//return.
function refreshGridData(searchString){
if (searchString =='undefined'){
searchString = "";
}
var xhr;
var gridData;
var url;
url = "DefaultHandler.ashx?partialUserFullName=" + escape(searchString);
xhr = GetXMLHttpRequestObject();
xhr.onreadystatechange = function() {
if (xhr.readystate==4) {
gridData = eval(xhr.responseText);
if (gridData.length > 0) {
//clear and fill the grid
clearAndPopulateGrid(gridData);
}
else {
//display appropriate message
}
} //if (xhr.readystate==4) {
} //xhr.onreadystatechange = function() {
xhr.open("GET", url, true);
xhr.send(null);
}
//this does the grid clearing and population, and enables the search button when complete.
function clearAndPopulateGrid(jsonObject) {
var grid = igtbl_getGridById('uwgUsers');
var eleBtn;
eleBtn = document.getElementById('btnSearch');
//clear the rows
for (x = grid.Rows.length; x >= 0; x--) {
grid.Rows.remove(x, false);
}
//add the new ones
for (x = 0; x < jsonObject.length; x++) {
var newRow = igtbl_addNew(grid.Id, 0, false, false);
//the cells should not be referenced by index value, so a name lookup should be implemented
newRow.getCell(0).setValue(jsonObject[x][1]);
newRow.getCell(1).setValue(jsonObject[x][2]);
newRow.getCell(2).setValue(jsonObject[x][3]);
}
grid = null;
eleBtn.disabled = false;
eleBtn.value = "Search by partial full name";
}
// this function will return the XMLHttpRequest Object for the current browser
function GetXMLHttpRequestObject() {
var XHR; //the object to return
var ua = navigator.userAgent.toLowerCase(); //gets the useragent text
try
{
//determine the browser type
if (!window.ActiveXObject)
{ //Non IE Browsers
XHR = new XMLHttpRequest();
}
else
{
if (ua.indexOf('msie 5') == -1)
{ //IE 5.x
XHR = new ActiveXObject("Msxml2.XMLHTTP");
}
else
{ //IE 6.x and up
XHR = new ActiveXObject("Microsoft.XMLHTTP");
}
} //end if (!window.ActiveXObject)
if (XHR == null)
{
throw "Unable to instantiate the XMLHTTPRequest object.";
}
}
catch (e)
{
alert("This browser does not appear to support AJAX functionality. error: " + e.name
+ " description: " + e.message);
}
return XHR;
} //end function GetXMLHttpRequestObject()
function trim(stringToTrim){
return stringToTrim.replace(/^\s\s*/, '').replace(/\s\s*$/, '');
}
And the ashx handler looks like this....
Imports System.Web
Imports System.Web.Services
Imports System.Data
Imports System.Data.SqlClient
Public Class DefaultHandler
Implements System.Web.IHttpHandler
Private Const CONN_STRING As String = "Data Source=;Initial Catalog=;User ID=;Password=;"
Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
context.Response.ContentType = "text/plain"
context.Response.Expires = -1
Dim strPartialUserName As String
Dim strReturnValue As String = String.Empty
If context.Request.QueryString("partialUserFullName") Is Nothing = False Then
strPartialUserName = context.Request.QueryString("partialUserFullName").ToString()
If String.IsNullOrEmpty(strPartialUserName) = False Then
strReturnValue = SearchAndReturnJSResult(strPartialUserName)
End If
End If
context.Response.Write(strReturnValue)
End Sub
Private Function SearchAndReturnJSResult(ByVal partialUserName As String) As String
Dim strReturnValue As New StringBuilder()
Dim conn As SqlConnection
Dim strSQL As New StringBuilder()
Dim objParam As SqlParameter
Dim da As SqlDataAdapter
Dim ds As New DataSet()
Dim dr As DataRow
'define sql
strSQL.Append(" SELECT ")
strSQL.Append(" [id] ")
strSQL.Append(" ,([first_name] + ' ' + [last_name]) ")
strSQL.Append(" ,[email] ")
strSQL.Append(" FROM [person] (NOLOCK) ")
strSQL.Append(" WHERE [last_name] LIKE @lastName")
'clean up the partial user name for use in a like search
If partialUserName.EndsWith("%", StringComparison.InvariantCultureIgnoreCase) = False Then
partialUserName = partialUserName & "%"
End If
If partialUserName.StartsWith("%", StringComparison.InvariantCultureIgnoreCase) = False Then
partialUserName = partialUserName.Insert(0, "%")
End If
'create the oledb parameter... parameterized queries perform far better on repeatable
'operations
objParam = New SqlParameter("@lastName", SqlDbType.VarChar, 100)
objParam.Value = partialUserName
conn = New SqlConnection(CONN_STRING)
da = New SqlDataAdapter(strSQL.ToString(), conn)
da.SelectCommand.Parameters.Add(objParam)
Try 'to get a dataset.
da.Fill(ds)
Catch sqlex As SqlException
'Throw an appropriate exception if you can add details that will help understand the problem.
Throw New DataException("Unable to retrieve the results from the user search.", sqlex)
Finally
If conn.State = ConnectionState.Open Then
conn.Close()
End If
conn.Dispose()
da.Dispose()
End Try
'make sure we have a return value
If ds Is Nothing OrElse ds.Tables(0) Is Nothing OrElse ds.Tables(0).Rows.Count <= 0 Then
Return String.Empty
End If
'This converts the table into JS array.
strReturnValue.Append("[")
For Each dr In ds.Tables(0).Rows
strReturnValue.Append("['" & CStr(dr("username")) & "','" & CStr(dr("userfullname")) & "','" & CStr(dr("useremail")) & "'],")
Next
strReturnValue.Remove(strReturnValue.Length - 1, 1)
strReturnValue.Append("]")
'de-allocate what can be deallocated. Setting to Nothing for smaller types may
'incur performance hit because of a forced allocation to nothing before they are deallocated
'by garbage collection.
ds.Dispose()
strSQL.Length = 0
Return strReturnValue.ToString()
End Function
ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
Get
Return False
End Get
End Property
End Class
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