Server.Transfer vs. Response.Redirect

A common misconception is the difference between Server.Transfer and Response.Redirect in ASP.NET applications. Redirect and Transfer both cause a new page to be processed, but the interaction between the client (web browser) and server (ASP.Net) is different in each situation.

Redirect:

A redirect is just a suggestion – it’s like saying to the client “Hey, you might want to look at this”. All you tell the client is the new URL to look at, and if they comply, they do a second request for the new URL.

If you want to pass state from the source page to the new page, you have to pass it either on the URL (such as a database key, or message string), or you can store it in the Session object (caveat: there may be more than one browser window, and they’ll all use the same session object).

e.g. Redirect to the new.aspx page, passing an ID on the query string. “true” stops processing the current page:

Context.Items["Message"] = “Response.Redirect(“new.aspx?id=34″, true);

Transfer:

A transfer happens without the client knowing – it’s the equivalent of a client requesting one page, but being given another. As far as the client knows, they are still visiting the original URL.

Sharing state between pages is much easier using Server.Transfer – you can put values into the Context.Items dictionary, which is similar to Session and Application, except that it lasts only for the current request. (search for HttpContext in MSDN). The page receiving postback can process data, store values in the Context, and then Transfer to a page that uses the values.

e.g. Store a message in the context dictionary, and transfer to the default.aspx page (which can then display the message):

Context.Items["Message"] = “Your password was changed successfully”;

Server.Transfer(“default.aspx”);

Caveats:

• Response.Redirect is more user-friendly, as the site visitor can bookmark the page that they are redirected to.
• Transferred pages appear to the client as a different url than they really are. This means that things like relative links / image paths may not work if you transfer to a page from a different directory.
• Server.Transfer has an optional parameter to pass the form data to the new page.
• Since the release version, this no longer works, because the Viewstate now has more security by default (The EnableViewStateMac defaults to true), so the new page isn’t able to access the form data. You can still access the values of the original page in the new page, by requesting the original handler:

Page originalPage = (Page)Context.Handler;

TextBox textBox1 = (TextBox)originalPage.FindControl(“textBox1″);

Using the window.open method

The syntax of the window.open method is given below:

open (URL, windowName[, windowFeatures])

URL
The URL of the page to open in the new window. This argument could be blank.

windowName
A name to be given to the new window. The name can be used to refer this window again.

windowFeatures
A string that determines the various window features to be included in the popup window (like status bar, address bar etc)

The following code opens a new browser window with standard features.

window.open ("http://www.javascript-coder.com","mywindow");

Note: The popups created using ‘window.open()’ can get blocked by popup blockers.
Click here to find out how to create popups that does not get blocked.

Changing the features of the Popup

You can control the features of the popup using the last argument to the window.open method. The following code opens a window with a status bar and no extra features.
window.open ("http://www.javascript-coder.com","mywindow","status=1");

The code below opens a window with toolbar and status bar.
window.open ("http://www.javascript-coder.com",
"mywindow","status=1,toolbar=1");

The table shows the features and the string tokens you can use:

status	The status bar at the bottom of the window.
toolbar	The standard browser toolbar, with buttons such as Back and Forward.
location	The Location entry field where you enter the URL.
menubar	The menu bar of the window
directories	The standard browser directory buttons, such as What’s New and What’s Cool
resizable	Allow/Disallow the user to resize the window.
scrollbars	Enable the scrollbars if the document is bigger than the window
height	Specifies the height of the window in pixels. (example: height=’350′)
width	Specifies the width of the window in pixels.

Examples
The following code opens a window with menu bar. The window is resizable and is having 350 pixels width and 250 pixels height.
window.open ("http://www.javascript-coder.com",
"mywindow","menubar=1,resizable=1,width=350,height=250");
Example 1

A window with location bar, status bar, scroll bar and of size 100 X 100
window.open ("http://www.javascript-coder.com",
"mywindow","location=1,status=1,scrollbars=1,
width=100,height=100");
Example 2

Moving the window to a desired location

You can use the window.moveTo function to move the popup window to a desired location.
The code below shows positioning the popup at a desired location

function mypopup()
{
mywindow = window.open ("http://www.javascript-coder.com",
"mywindow","location=1,status=1,scrollbars=1,
width=100,height=100");
mywindow.moveTo(0,0);
}
The code positions the popup on the top left corner of the screen.

Putting it all together

Now we will combine all these information to create the popup windows of different types.
The Code below opens a popup window when you enter the page:

<html>
<head>
<title>JavaScript Popup Example 3</title>
</head>
<SCRIPT language="JavaScript1.2">
function poponload()
{
testwindow= window.open ("", "mywindow",
"location=1,status=1,scrollbars=1,width=100,height=100");
testwindow.moveTo(0,0);
}
</SCRIPT>
<body onload="javascript: poponload()">
<H1>JavaScript Popup Example 3</H1>
</body>
</html>

Notice that the URL is kept blank. This will open a blank window. You can see the code in work in this file:
JavaScript Popup Example 3

Popup On Exit

The following code pops up a window when the user exits a page.

<html>
<head>
<title>JavaScript Popup Example 3</title>
</head>
<SCRIPT language="JavaScript1.2">
function exitpop()
{
my_window= window.open ("",
"mywindow1","status=1,width=350,height=150");
my_window.document.write('<H1>Popup Test!</H1>');
}
</SCRIPT>
<body onunload="javascript: exitpop()" >
<H1>JavaScript Popup Example 4</H1>
</body>
</html>

The code contains an extra line:
my_window.document.write('<H1>Popup Test!</H1>')
This code displays a line ‘Popup Test!’ in the popup.

Cursors: An Overview

SQL Server is very good at handling sets of data. For example, you can use a single UPDATE statement to update many rows of data. There are times when you want to loop through a series of rows a perform processing for each row. In this case you can use a cursor.

DECLARE @AuthorID char(11)

DECLARE c1 CURSOR READ_ONLY
FOR
SELECT au_id
FROM authors

OPEN c1

FETCH NEXT FROM c1
INTO @AuthorID

WHILE @@FETCH_STATUS = 0
BEGIN

PRINT @AuthorID

FETCH NEXT FROM c1
INTO @AuthorID

END

CLOSE c1
DEALLOCATE c1