HttpWebRequest to ASPX for Postback

  • Thread starter Thread starter TJO
  • Start date Start date
T

TJO

I am working with the HttpWebRequest agains a simple aspx page that I
created. The page has two panels one for the input of two html input boxes
and the secone panel that displays the values of the input boxes on
postback.

I make my first web GET request like this:
objRequest1 = (HttpWebRequest)System.Net.HttpWebRequest.Create(uri);
objRequest1.Method = "GET";
objRequest1.ContentType = "text/html";
objRequest1.CookieContainer = new CookieContainer();
objRequest1.AllowAutoRedirect = true;

objResponse1 = (HttpWebResponse)objRequest1.GetResponse();
sr = new StreamReader(objResponse1.GetResponseStream());
result = sr.ReadToEnd();
sr.Close();

I then receive a session cookie that I put in my 2nd request like this:

string postData = "txt_name=tim&txt_address=261 Trailway"

objRequest2 = (HttpWebRequest)System.Net.HttpWebRequest.Create(uri);
objRequest2.Method = "POST";
objRequest2.AllowAutoRedirect = true;
objRequest2.ContentLength = postData.Length;
objRequest2.ContentType = "application/x-www-form-urlencoded";
objRequest2.Timeout = 100000;
objRequest2.CookieContainer = new CookieContainer();
objRequest2.CookieContainer.Add(objResponse1.Cookies);
myWriter = new StreamWriter(objRequest2.GetRequestStream());
myWriter.Write(postData);

objResponse2 = (HttpWebResponse)objRequest2.GetResponse();
sr = new StreamReader(objResponse2.GetResponseStream());
result = sr.ReadToEnd();
sr.Close();

I am hoping this 2nd request trigger the postback and therefore the output
data in the 2nd panel but it does not. What am I doing wrong?

Thank for you help.
 
"TJO" spoke:
I am working with the HttpWebRequest agains a simple aspx page that I
created. The page has two panels one for the input of two html
input boxes and the secone panel that displays the values of the
input boxes on postback.

I make my first web GET request like this:
objRequest1 = (HttpWebRequest)System.Net.HttpWebRequest.Create(uri);
objRequest1.Method = "GET";
objRequest1.ContentType = "text/html";
objRequest1.CookieContainer = new CookieContainer();
objRequest1.AllowAutoRedirect = true;

objResponse1 = (HttpWebResponse)objRequest1.GetResponse();
sr = new StreamReader(objResponse1.GetResponseStream());
result = sr.ReadToEnd();
sr.Close();

I then receive a session cookie that I put in my 2nd request like
this:

string postData = "txt_name=tim&txt_address=261 Trailway"

objRequest2 = (HttpWebRequest)System.Net.HttpWebRequest.Create(uri);
objRequest2.Method = "POST";
objRequest2.AllowAutoRedirect = true;
objRequest2.ContentLength = postData.Length;
objRequest2.ContentType = "application/x-www-form-urlencoded";
objRequest2.Timeout = 100000;
objRequest2.CookieContainer = new CookieContainer();
objRequest2.CookieContainer.Add(objResponse1.Cookies);
myWriter = new StreamWriter(objRequest2.GetRequestStream());
myWriter.Write(postData);

objResponse2 = (HttpWebResponse)objRequest2.GetResponse();
sr = new StreamReader(objResponse2.GetResponseStream());
result = sr.ReadToEnd();
sr.Close();

I am hoping this 2nd request trigger the postback and therefore the
output data in the 2nd panel but it does not. What am I doing wrong?
Click to expand...

Cut and pasting myself again...

Your requested Content-Length will *never* match the actual
Content-Length. That's because you use a StreamWriter constructor that
implicitly uses UTF-8 encoding (good) but prepends the UTF-8 byte order
mark at the beginning of the transmitted string (bad). It gets worse if
"postData " contains non 7-bit characters such as a German umlaut. These
characters may take two ore more bytes to encode. The harmless string
Name=Jörg will take 3 (BOM) + 9 (string length) + 1 (additonal byte to
encode the 'ö') = 13 bytes to send, but your code will say it's only 9
bytes.

Morale of the story: Encode the string yourself using an appropriate
encoding object, measure the resulting byte array's size (that's your
real Content-Length) and write it directly to the request stream:

// This constructor supresses the BOM
Encoding utf8 = new UTF8Encoding();
// Encode string manually
byte[] content = utf8.GetBytes(strPost);
// Set header
request.ContentLength = content.Length;

// Now, use Stream.Write to write the bytes to the request stream
using (Stream requestStream = request.GetRequestStream())
{
requestStream.Write(content, 0, content.Length);
}

Your code also neither explictly calls Close() nor Flush() on the
writer.

Cheers,
 
Thanks Joerg,
I have added the code you suggested but my same problem persists. Why is my
second request not initiating the Postback to my target web form?


Joerg Jooss said:
"TJO" spoke:
I am working with the HttpWebRequest agains a simple aspx page that I
created. The page has two panels one for the input of two html
input boxes and the secone panel that displays the values of the
input boxes on postback.

I make my first web GET request like this:
objRequest1 = (HttpWebRequest)System.Net.HttpWebRequest.Create(uri);
objRequest1.Method = "GET";
objRequest1.ContentType = "text/html";
objRequest1.CookieContainer = new CookieContainer();
objRequest1.AllowAutoRedirect = true;

objResponse1 = (HttpWebResponse)objRequest1.GetResponse();
sr = new StreamReader(objResponse1.GetResponseStream());
result = sr.ReadToEnd();
sr.Close();

I then receive a session cookie that I put in my 2nd request like
this:

string postData = "txt_name=tim&txt_address=261 Trailway"

objRequest2 = (HttpWebRequest)System.Net.HttpWebRequest.Create(uri);
objRequest2.Method = "POST";
objRequest2.AllowAutoRedirect = true;
objRequest2.ContentLength = postData.Length;
objRequest2.ContentType = "application/x-www-form-urlencoded";
objRequest2.Timeout = 100000;
objRequest2.CookieContainer = new CookieContainer();
objRequest2.CookieContainer.Add(objResponse1.Cookies);
myWriter = new StreamWriter(objRequest2.GetRequestStream());
myWriter.Write(postData);

objResponse2 = (HttpWebResponse)objRequest2.GetResponse();
sr = new StreamReader(objResponse2.GetResponseStream());
result = sr.ReadToEnd();
sr.Close();

I am hoping this 2nd request trigger the postback and therefore the
output data in the 2nd panel but it does not. What am I doing wrong?
Click to expand...

Cut and pasting myself again...

Your requested Content-Length will *never* match the actual
Content-Length. That's because you use a StreamWriter constructor that
implicitly uses UTF-8 encoding (good) but prepends the UTF-8 byte order
mark at the beginning of the transmitted string (bad). It gets worse if
"postData " contains non 7-bit characters such as a German umlaut. These
characters may take two ore more bytes to encode. The harmless string
Name=Jörg will take 3 (BOM) + 9 (string length) + 1 (additonal byte to
encode the 'ö') = 13 bytes to send, but your code will say it's only 9
bytes.

Morale of the story: Encode the string yourself using an appropriate
encoding object, measure the resulting byte array's size (that's your
real Content-Length) and write it directly to the request stream:

// This constructor supresses the BOM
Encoding utf8 = new UTF8Encoding();
// Encode string manually
byte[] content = utf8.GetBytes(strPost);
// Set header
request.ContentLength = content.Length;

// Now, use Stream.Write to write the bytes to the request stream
using (Stream requestStream = request.GetRequestStream())
{
requestStream.Write(content, 0, content.Length);
}

Your code also neither explictly calls Close() nor Flush() on the
writer.

Cheers,
Click to expand...
 
"TJO" spoke:
Thanks Joerg,
I have added the code you suggested but my same problem persists.
Why is my second request not initiating the Postback to my target
web form?
Click to expand...

Hm, if that is a ASP.NET web form, you probably need to include some
more information in the request like the pressed button and the
viewstate.

Cheers,
 
The Solution is Here

Hello Guys ,

The ASPX Page realizes the PostBack with the Help of the Three Parameters along with the Post back values that u want to submit to the ASPX Page.

For the ASPX Page to recognize the PostBack , first it checks for the Valid ViewState of that Page.

Step1: So guys get the ViewState of the Page at the time of the Page Load using the Get Method

You will need to provide the ViewState as a PostBack Parameter as __VIEWSTATE=viewState(that u just got).

The ASPX Page now requires the Two more parameters to know what trigerred the PostBack.
The first Parameter is the __EVENTTARGET that takes the ID of the Control that trigerred the PostBack and the __EVENTARGUMENT that has the argument values of the Control

Step2: U need to provide the values og the __EVENTTARGET and the __EVENTARGUMENT externally in the PostBack data string

So the final string that u write using the StreamWriter will look like this

string PostBack = String.Format("__VIEWSTATE={0}&__EVENTTARGET={1}&__EVENTARGUMENT={2}&username=asdf&password=12345",viewState,ControlID,"");

This will surely raise the Post Back at the ASPX Page.
 
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