Introduction
There are many reasons to upgrade
your existing 'legacy' Web Forms applications. One
of the main reasons would be performance.
Are your pages just taking too long to load? Is every form submit taking more than a few
seconds to respond? Users will usually
get frustrated at this, especially if there is no 'Loading' panel or other visual
indicator. This is usually the sign of a
web application that was not written from the ground up to be as fast as
possible. Web Forms apps (written in the
standard way) with very 'heavy' pages will take a long time to load every time
the user interacts with a page. This is
usually because of the fact that a postback is actually occurring. A postback is when the user presses a submit
button somewhere on the form, and the entire page, is sent to the server, but
more importantly, the entire page is again written back from the server, which
causes a 'double whammy' effect of very slow page load times. These applications can usually be quickly
changed to use lightweight javascript libraries, along with Web services, as a
way to request and submit data from the page.
In this way, only the minimum amount of data is actually loaded, and
sent back and forth to the server. So,
every time a user loads a page or performs any action requiring data to be sent
back and forth to the server, only the essential data is sent back and forth,
and not the entire page.
Save
time and money by NOT rewriting your application
Resist the urge to re-write the
entire application. Why? Just for a refresher, read Joel Spolsky’s classic
article: Things you should never do, Part 1. There may be some extreme cases where a re-write is the
best option, but 99% of the time a re-write is a big mistake. After thinking of one of the main reasons why
not to rewrite, it should be clear:
You've already spent a long time (perhaps years) refining your Business
logic, fixing many bugs, and improving your underlying database performance, so
why start from scratch and have to do it all over again?
Most ASP.NET Web Forms applications
consist of a number of ASP.NET (or third party controls such as Infragistics or
Telerik), which are simply dropped on the form, and used with a few statements
in codebehind (aspx.vb or aspx.cs). This
makes it easy for developers with only a basic understanding of the application
to quickly cut and paste code into an existing app. This usually leads to poor coding practices,
and poor performance. Some controls such
as Update Panels make it very tempting to simply drop on the page and allow
.NET to take care of the rest.
Using the code
As a quick example, I created an
ASP.NET page with a standard UpdatePanel, and codebehind. The UpdatePanel is usually used to eliminate
any screen refreshes occurring with a full page postback:
default.aspx:
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<asp:UpdatePanel runat="server" ID="up1">
<ContentTemplate>
<asp:Label runat="server" ID="Label1" Text="Update Me!" /><br />
<asp:Button runat="server" ID="Button1"
Text="Postback Update" OnClick="Button1_Click" />
</ContentTemplate>
</asp:UpdatePanel>
default.aspx.cs: protected void Button1_Click(object sender, EventArgs e)
{
Label1.Text = DateTime.Now.ToLongDateString();
}
Simple
enough. Button1 is clicked, an asynchronous request is made for the current
date/time, and that is displayed as Label1′s content. As simple as it sounds,
take a look at the actual HTTP post and response necessary to accomplish the
partial postback:
That’s
a LOT of data sent back and forth to the web server just to display a 16
character string! This may be acceptable
for infrequently used functionality, but, not in a heavily used production
system. Luckily, Microsoft has given us a more efficient way to do this, as
part of the ASP.NET AJAX framework.
Page
Methods
Page
methods allow ASP.NET AJAX pages to directly execute a page’s static methods
using JSON (JavaScript Object
Notation). JSON is basically a minimalistic version of SOAP, which is perfectly
suited for light weight communication between client and server. For more
information about how to implement page methods and JSON, take a look at
Microsoft’s Exposing Web Services to Client Script in ASP.NET AJAX.
Instead of performing a partial postback and
then receiving HTML markup to completely replace our UpdatePanel’s contents, we
can use a web method to request only the information that we’re interested in: default.aspx:
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true" />
<script language="javascript">
function UpdateTime() {
PageMethods.GetCurrentDate(OnSucceeded, OnFailed);
}
function OnSucceeded(result, userContext, methodName) {
$get('Label1').innerHTML = result;
}
function OnFailed(error, userContext, methodName) {
$get('Label1').innerHTML = "An error occured.";
}
</script>
<asp:Label runat="server" ID="Label1" Text="Update Me!" /><br />
<input type="button" id="Button2" value="Web Method Update"
onclick="UpdateTime();" />
default.aspx.cs:
[WebMethod]
public static string GetCurrentDate()
{
return DateTime.Now.ToLongDateString();
}
Through
this method, we’ve completely eliminated the extra data that was present in the
UpdatePanel’s request, and reduced the response down to just the data we’re
interested in requesting:
Using
JSON, the entire HTTP round trip is 16 bytes, as compared to 872 bytes for the
UpdatePanel. That’s roughly a 5,000% improvement!!, which will only continue to
increase with the complexity of the page.
Not only has this reduced our network footprint dramatically, but it
eliminates the necessity for the server to instantiate the UpdatePanel’s
controls and take them through their life cycles to render the HTML sent back
to the browser. While I’m a proponent of
the simplicity inherent in the UpdatePanel, I think that it is crucial that we
use them judiciously. In any heavy use situation, they are very rarely the best
solution.
Ease of Development
As a seasoned WebForms developer, you may be thinking: "Wow, now I have to learn how to use
these new fangled javascript libraries."
Or, "Now we have to spend a lot of time redoing every page with
these new low level javascript functions which we've never used!" But, wait, there is an easy to use
alternative that has both high performance and ease of use. I've used JQuery, KendoUI, Knockout, and
other high level javascript libraries to create some amazing applications such
as a mapping application (allowing drag and drop between 2 maps on a page), Dashboard
applications with full graphing capabilities, an Excel-like editable grid, and
more, all in a matter of weeks. The
power, speed and control you have with these high level javascript libraries
are far and above that of standard WebForms development. Your code will be cleaner, and there will be
no need to handle control from server side code to client side code, and vice
versa, as all your UI coding will be in Javascript. As an example, I created a high performance Auditing
'History' page, which is entirely in Jquery and Javascript to replace an
existing History Page in an ASP.NET WebForms application:
The History screen has all the features you’d expect in a
typical Auditing / History form.
Implemented features are: Search / Filter, Sort, Number of entries per
page, “ToolTips” for extra long field data, and a cool feature that allows the
user to get rid of NULL-Blank ‘transitions’, eliminating unnecessary records
being displayed. Your aspx / ascx page
would consist of a div which the Jquery code will create the grid from, along
with the appropriate Javascript function to call the display grid function:
function showHistory() {
var contractkey = $("#<%= hdnCID.ClientID %>").val();
var type = 0;
var checked = $("#chkFilterBlank").prop("checked");
displayHistory(type, contractkey, checked);
}
<div id="divHistory" style="width: 900px; height: 540px; background-color: #EDECEB; display: none;">
<table id="tblHistory" class="display" cellspacing="0" cellpadding="0" border="0" style=" margin: 5px 25px 0px 0px; color:#000000; border: 1px solid #222222;">
</table><br />
<input type="checkbox" id="chkFilterBlank" checked="checked" name="filterblank" value="filter"/>Filter Blank transitions
<input id="btnRefresh" type="button" class="button-right" value="refresh" runat="server" onclick="showHistory(); return false;" />
</div>
The external history.js javascript
file consists of the actual function to create the grid. I used the ‘datatables’
plugin in this case, which performs fast server-side paging, allowing the history
form to be extremely fast (< 1 second response time on any load, search, sort, page,
or refresh operation.):
function displayHistory(type, id, filterblank) {
try {
if (filterblank == undefined || filterblank == null)
filterblank = true;
showHistoryDialog();
var oTable = $('#tblHistory').dataTable(
{
"bDestroy": true,
"bJQueryUI": true,
"bSort": true,
"bAutoWidth": true,
"bProcessing": true,
"bServerSide": true,
"sScrollX": "1500px",
"sScrollY": "385px",
"sPaginationType": "full_numbers",
"iDisplayLength": 15,
"aLengthMenu": [[10, 15, 25, 50, 100], [10, 15, 25, 50, 100]],
"sAjaxSource": "AjaxPage.aspx",
"fnServerParams": function (aoData) {
aoData.push({ "name": "type", "value": type },
{ "name": "rowId", "value": id },
{ "name": "filterBlank", "value": filterblank },
{ "name": "CallRequest", "value": "ProcessHistory" });
},
"aoColumnDefs": [
{ "sTitle": "Table", "sWidth": "160px", "type": "text", "aTargets": [0] },
{ "sTitle": "Column", "sWidth": "110px", "type": "text", "aTargets": [1],
"fnCreatedCell": function (nTd, sData, oData, iRow, iCol) {
$(nTd).attr('title', oData[6]);
}
},
{ "sTitle": "Old Value", "sWidth": "110px", "type": "text", "aTargets": [2],
"fnCreatedCell": function (nTd, sData, oData, iRow, iCol) {
$(nTd).attr('title', oData[7]);
}
},
{ "sTitle": "New Value", "sWidth": "110px", "type": "text", "aTargets": [3],
"fnCreatedCell": function (nTd, sData, oData, iRow, iCol) {
$(nTd).attr('title', oData[8]);
}
},
{ "sTitle": "Changed", "sWidth": "195px", "sType": "date", "aTargets": [4] },
{ "sTitle": "Changed By", "sWidth": "140px", "type": "text", "aTargets": [5] }
]
});
}
catch (exception) {
}
}
Your Server side code could be an
.asmx page, .ashx page (.NET Handler), or even an .aspx page. In this case, I’ve used an .aspx page which
acts the same as a typical codebehind aspx.vb page, except that I don’t handle
any postbacks, only HTTP Requests. I’m
using the “GET” method, as this particular Jquery plug-in (Datatables.net)
implements this method when using the server-side paging functionality:
Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim callRequest As String = If((Me.Request("CallRequest") Is Nothing), String.Empty, Me.Request("CallRequest"))
Dim dataTable As DataTable = Nothing
Dim returnValue As Boolean = False
Dim strJson = Nothing
If callRequest = "ProcessHistory" Then
strJson = ProcessHistory()
End If
Me.Response.ClearHeaders()
Me.Response.Clear()
Me.Response.ContentType = "application/json"
Me.Response.Write(strJson)
Me.Response.[End]()
End Sub
Public Function ProcessHistory() As String
Try
Dim iDisplayLength = Integer.Parse(HttpContext.Current.Request.QueryString("iDisplayLength"))
Dim iDisplayStart = Integer.Parse(HttpContext.Current.Request.QueryString("iDisplayStart"))
Dim iSortCol = Integer.Parse(HttpContext.Current.Request.QueryString("iSortCol_0"))
Dim iSortDir = HttpContext.Current.Request.QueryString("sSortDir_0")
Dim sSearch = HttpContext.Current.Request.QueryString("sSearch")
Dim type = Integer.Parse(HttpContext.Current.Request.QueryString("type"))
Dim rowId = Integer.Parse(HttpContext.Current.Request.QueryString("rowId"))
Dim filterBlank = Boolean.Parse(HttpContext.Current.Request.QueryString("filterBlank"))
Dim sEcho = HttpContext.Current.Request.QueryString("sEcho")
Dim history = TryCast(TableAudit.GetTableHistory(DirectCast(type, TableHistoryType), rowId), IEnumerable(Of TableHistoryResult))
If filterBlank = True Then
Dim historylist As List(Of TableHistoryResult) = TryCast(history, List(Of TableHistoryResult))
historylist.RemoveAll(AddressOf IsBlankTransition)
End If
Dim order As Func(Of TableHistoryResult, Object) = Function(hist)
Select Case iSortCol
Case 0
Return DirectCast(hist.TableName, Object)
Case 1
Return DirectCast(hist.ColumnName, Object)
Case 2
Return DirectCast(hist.OldValue, Object)
Case 3
Return DirectCast(hist.NewValue, Object)
Case 4
Return DirectCast(hist.ChangedDateTime, Object)
Case Else
Return DirectCast(hist.UserChangedByLoginName, Object)
End Select
End Function
history = If("desc" = iSortDir, history.OrderByDescending(order), history.OrderBy(order))
sSearch = sSearch.ToLower()
history = history.Where(Function(h) (h.TableName IsNot Nothing AndAlso h.TableName.ToLower().Contains(sSearch)) OrElse (h.ColumnName IsNot Nothing AndAlso h.ColumnName.ToLower().Contains(sSearch)) OrElse (h.OldValue IsNot Nothing AndAlso h.OldValue.ToLower().Contains(sSearch)) OrElse (h.NewValue IsNot Nothing AndAlso h.NewValue.ToLower().Contains(sSearch)) OrElse (h.UserChangedByLoginName IsNot Nothing AndAlso h.UserChangedByLoginName.ToLower().Contains(sSearch)))
Dim aaData2 = history.[Select](Function(h) New With {h.TableName, .ColBlank = h.ColumnName.Substring(0, Math.Min(h.ColumnName.Length, 6)) + (If(h.ColumnName.Length <= 6, "", "...")), _
.OldBlank = If(h.OldValue Is Nothing, "", (h.OldValue.Substring(0, Math.Min(h.OldValue.Length, 6)) + (If(h.OldValue.Length <= 6, "", "...")))), _
.NewBlank = If(h.NewValue Is Nothing, "", (h.NewValue.Substring(0, Math.Min(h.NewValue.Length, 6)) + (If(h.NewValue.Length <= 6, "", "...")))), _
.ChangedDateTime = h.ChangedDateTime.ToString("yyyy-MM-ddTHH:mm:ssZ"), _
h.UserChangedByLoginName, _
h.ColumnName, h.OldValue, h.NewValue}).Skip(iDisplayStart).Take(iDisplayLength)
Dim lsthistory As New List(Of String())
For Each historyitem In aaData2
Dim arrHistory As String() = New String(8) {historyitem.TableName,
historyitem.ColBlank,
historyitem.OldBlank,
historyitem.NewBlank,
historyitem.ChangedDateTime,
historyitem.UserChangedByLoginName,
historyitem.ColumnName,
historyitem.OldValue,
historyitem.NewValue}
lsthistory.Add(arrHistory)
Next
Dim result = New With { _
Key .sEcho = sEcho, _
Key .iTotalRecords = history.Count(), _
Key .iTotalDisplayRecords = history.Count(), _
Key .aaData = lsthistory
}
Dim json = SerializeToJSON(result)
Return json
Catch ex As Exception
End Try
End Function
Note the use of VB.NET, LINQ and anonymous
types (VB.NET handles anonymous type declaration differently than C#.). You can simply use a call to your existing
data layer, instead of the use of LINQ as I did in this example.
Updating your existing application
The
above examples demonstrated how to simply replace your UI code with Javascript
/ Jquery. So, there would be no need to
rewrite your entire application just to improve the performance and
maintainability of your system. You can apply either technique learned in this article, depending on the structure of your application to achieve a massive reduction in data sent back and forth between the application.
You may
choose to simply upgrade your UI portion of your code, or even to use MVC. With the .NET Framework 4.5.1, you can even
add MVC into your existing WebForms application
without having to start from scratch.
This will allow you to reuse all of your existing business logic, and
only upgrade a few areas of your site at a time, while keeping your MVC code
separate from your existing WebForms pages.