When we add a web reference to a web service behind the screen wsdl.exe is run which creates the proxy class. Proxy class contains both synchronous and asynchronous flavors of each web method.For simple HelloWorld() web method following methods are there in the proxy class

Public string HelloWorld()

Public string HelloWorldAsync();

Public string HelloWorldAsync(object userState);

We call the HelloWorldAsync() method which in turn calls the following method of the proxy class InvokeAsync()

// Summary:

// Invokes the specified method asynchronously.

// Parameters:

// methodName:

// The name of the method to invoke.

// parameters:

// The parameters to pass to the method.

// callback:

// The delegate called when the method invocation has completed.

protected void InvokeAsync(string methodName, object[] parameters, SendOrPostCallback callback);

HelloWorldCompletedEventArgs– This class is also created by wsdl.exe which contains the result of our operation.

Suppose this is our simple web service, we have introduced delay to understand the asynchronous behavior.

[WebMethod]

public string HelloWorld() {

Thread.Sleep(5000);

return “Hello World”;

}

Now to call the above webservice method asynchrously in a windows application client we need to do the following

Say we have want to call the HelloWorld method asynchronously on the click of the button,

private void btnCallService_Click(object sender, EventArgs e)

{

// Create the instance of the proxy class

Service myService = new Service();

// Register an eventhandler for HelloWorldCompleted event

// The eventhandler would be called when the request is

// completed

myService.HelloWorldCompleted += new

HelloWorldCompletedEventHandler(this.HelloWorldCompleted);

// instead of calling the synchronous HelloWorld() we need

// to call the HelloWorldAsync() method

myService.HelloWorldAsync();

}

void HelloWorldCompleted(object sender,HelloWorldCompletedEventArgs args){

// Display the reutrn value

MessageBox.Show(args.Result);

}

To call the above web method in an asp.net client we need to add the following attribute in the @Page directive

Async=”true”

Bye..

By default, ASP.NET permits only files that are 4,096 kilobytes (KB) or less to be uploaded to the Web server.  To upload larger files, we must change the maxRequestLength parameter of the <httpRuntime> section in the Web.config file. By default, the <httpRuntime> element is set to the following parameters in the Machine.config file:

<httpRuntime

executionTimeout=“90“

maxRequestLength=“4096“

useFullyQualifiedRedirectUrl=“false“

minFreeThreads=“8“

minLocalRequestFreeThreads=“4“

appRequestQueueLimit=“100“

/>

We can change the value of maxRequestLength to a desired value in our web.config of the application. For 10 mb we can set it to 10240 KB. Even in this case if user tries to upload a file with size more than 10 mb we than get the above “Page cannot be displayed error ” or the page simply hang up. In this case we can catch the error in the Application_Error event handler of the Global.asax file.

void Application_Error(object sender, EventArgs e)

{

if (System.IO.Path.GetFileName(Request.Path) == “Default.aspx”)

{

System.Exception appException = Server.GetLastError();

if (appException.InnerException.Message == “Maximum request length exceeded.”)

{

Server.ClearError();

Response.Write(“The form submission cannot be processed because it exceeded the maximum length allowed by the Web administrator. Please resubmit the form with less data.”);

Response.Write(“<BR><a href=’Default.aspx’>Click Here to go back to page</a> </BR>”);

Response.End();  } } }

I tried with the above code, but it isn’t consistent.

The best solution for this could be to set the value of maxRequestLength to a very high value.

and checking in the code for the size.

Say changing the value to say 700mb ( not sure what the maximum length of request could be)

<httpRuntime useFullyQualifiedRedirectUrl=“true“

maxRequestLength=“716800“

/>

And checking for the length in your code

// Putting the constraint of 1 mb

if (FileUpload1.FileContent.Length < 1024){

FileUpload1.SaveAs(@”C:/MyFolder/” + FileUpload1.FileName);}

else{

return;}

At least the above solution would save us from the page not displayed error.

And the last solution which i found was creating an httpmodule to intercept the web request.

using System;

using System.Collections.Generic;

using System.Text;

using System.Web;

namespace HAMModule{

public class MyModule : IHttpModule{

public void Init(HttpApplication app){

app.BeginRequest += new EventHandler(app_BeginRequest);

}

void app_BeginRequest(object sender, EventArgs e){

HttpContext context = ((HttpApplication)sender).Context;

// check for size if more than 4 mb

if (context.Request.ContentLength > 4096000){

IServiceProvider provider = (IServiceProvider)context;

HttpWorkerRequest wr = (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));

// Check if body contains data

if (wr.HasEntityBody()){

// get the total body length

int requestLength = wr.GetTotalEntityBodyLength();

// Get the initial bytes loaded

int initialBytes = wr.GetPreloadedEntityBody().Length;

if (!wr.IsEntireEntityBodyIsPreloaded()){

byte[] buffer = new byte[512000];

// Set the received bytes to initial bytes before start reading

int receivedBytes = initialBytes;

while (requestLength – receivedBytes >= initialBytes){

// Read another set of bytes

initialBytes = wr.ReadEntityBody(buffer, buffer.Length);

// Update the received bytes

receivedBytes += initialBytes;

}

initialBytes = wr.ReadEntityBody(buffer, requestLength – receivedBytes);}}

// Redirect the user to an error page.

context.Response.Redirect(“Error.aspx”);}}

public void Dispose(){}

}}

and add the following information to web.config

<httpModules>

<add type=“HAMModule.MyModule“ name=“MyModule“/>

</httpModules>

inside

<system.web>

The last solution worked properly!!!!

BeginRequest event –The BeginRequest event signals the creation of any given new request. This event is always raised and is always the first event to occur during the processing of a request.

Article on creating a custom http module

http://msdn.microsoft.com/en-us/library/ms227673(VS.80).aspx

Bye..