I was asked how to get username in domain using ASP.NET.
My answer was:

string user = Page.User.Identity.Name;

As it didn't work, I tried to change it to the second version:

string user = System.Security.Principal.WindowsIdentity.GetCurrent().Name;

The second version did not work as well. Then I continued seeking for the problem. Finally I found a checkbox in the property pages of the web site that was the project published under. Check box was saying that anonymous access is allowed. Turning off the checkbox made both versions work correctly.
Also have in mind, your web configuration file must contain the following:

<system.web>
<configuration>
<identity impersonate="true" />
</configuration>
</system.web>

That's all.

Could not load file or assembly ‘[assembly name]' or one of its dependencies. Access is denied.

This error was showing up when trying to build a solution.
When googling you can find several solutions. In my case, the reason was an Antivirus software. I just disabled the access protection to the folder
‘C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files'.

All worked.

Why we need it? - In order to make some programmatic changes to the page. Have in mind - it works on the client side that means no JavaScript can be executed on the server. In general terms, that means, JavaScript does not do any server works like connecting to the database, calculating user rights, etc.
But there are several exceptions. For example, there are special ways for JavaScript to connect to the database, like using some special object types, or dlls. They can be used in JavaScript like assemblies that contain definitions of objects for implementing some logic of works. My own mind is, it's not correct to use such decisions in your work, because someone can view your JavaScript code as it's written down in clear way to the client browser. And of course, if you have written SQL database name, server name, username and password in clear format, it's not secure as you already understand.
Some other exceptions: JavaScript can be encrypted so that a general user of browser can not read your JavaScript code, as it's converted to some special character set, not recognizable for human eyes. But this kind of decision also contains some risk. There are a ways to decrypt back your encrypted code. Are you ready to take all the risk on your own? (But encrypting your code makes it a little harder for other coders to take your code and use it in their projects. It's useful if your code contains some high-intellectual logic that you don't want others to see and to still for example)

So, in general, JavaScript is used to make some little logical works on the client side, also for designing purposes, for example changing background color dynamically, or as an answer on some client action, not refreshing all the page.

Have you ever heard about AJAX technology? - A technology that is in most cases used to refresh some client area without refreshing the entire page. AJAX technology mainly uses JavaScript, in other words it automatically generates a JavaScript code to the client browser. But don't take too much; it doesn't make any server-side works at client side. For example if AJAX is used to collapse some part of page and expand another one, it's executed fully at client side, without refreshing the page. But if you use AJAX for refreshing the client area that contains exchange rates, and those rates are loaded from the database, then it will work fine, but not only at client side. In this case Page's Load event occurs also. But that little mechanism that sends the request to the server and then handles the request and refreshes the little area on the page, that's exactly a JavaScript, and acts as a part of AJAX generally.

How to learn it? Have a look at Microsoft Developer Network (MSDN) Library (http://msdn.microsoft.com).

Why I wrote this? I just opened internet explorer and hit Escape button as I saw browser was trying to enter my home page. Page loading process canceled and displayed the message, and a little link, possibly automatically generated by the browser, saying "click here to refresh", displaying a JavaScript code on mouse-over:

"javascirpt:location.replace("http://MyHomePage")".

Good JavaScript sample to begin with. Give a little attention to it and you will understand it's very useful.

And have in mind, here I've mentioned a fact that is often forgotten by the coders: even refreshing only a little part of ASP.NET page using AJAX, it makes a whole page to reload, and all the code contained in Page_Load event handler is executed.

Thank you for your time.

I decided to make a next step in researching the ASP.NET calendar control. I've used it several times, but never could find the way how I could change the navigate URLs that is navigated when the user clicks a day on the calendar control.

One decision that I have seen, is to create a user control for calendar, and then hard code all the logic in it. It's the same as to create a bicycle when it already exists. No, thanks.

And this time I just started searching through Google. Found something. One guy wrote on his blog, how to change background colors of the cells of calendar control. Really good work. The only thing you have to remember is a DayRender event of calendar control.
But one moment, the author of that blog shows us how to handle that event and write our logic. But it all's done outside of the control. When should we do so and when should we inherit from the control? Let's think.
Few weeks ago I have created a user control, which contains a calendar control, in this case sure, I really prefer to write the logic of the event handling outside the calendar control, because, anyway, this logic is placed inside the user control. I think it's a good manner to have all the logic inside the object that can be used repeatedly on your site and anywhere in the project, or other projects.
But if you don't need a user control, then I advice you to create a class, inherited from System.Web.UI.Calendar control class, and write all the logic inside that class. In other words you will need to override a method called OnDayRender. Then, in your page you will need to add a <%@ Register%> directive. And then, the most pleasant thing: change <asp.Calendar> tag with your one. I mean, "Register" directive requires you to register some TagPrefix that is associated with a namespace containing your calendar control. For example, if you created a class MyCalendar and it's contained in the namespace MyControls, then you will explicitly register that namespace with some TagPrefix. Let's say that tag prefix is "mc", then you will have to change <asp:Calendar> tags with this one "<mc:MyCalendar>". Of course you need to change only those calendar controls, which you want to extend with your logic, written in your code.

One interesting note: it doesn't break a design mode of your pages.
That means, All's OK!

... And let's return from the off-topic. I hope it was at least interesting.
We already understand where to handle the DayRender event.

DayRender (or OnDayRender) method has very useful parameters. I will consider an overridden method here; the same can be said about an event handler that can be implemented outside the class inherited from the Calendar control class.

protected override void OnDayRender(TableCell cell, CalendarDay day)

This will be the title of your method. You would think that our solution is under using variable day. I would think so also. But no. A day variable just contains information about a day that is to be rendered. You can change its properties, such as day.IsSelectable etc. But nothing to overwrite the navigate URL of the day. It's possible to do using cell variable. In this case, cell is a simple table cell. A calendar in general, is a table, which contains cells of course. cell variable is empty on this step. But one interesting thing is, if you assign something to the cell.Text property, it will remain it's value, and will not become something like just clickable number.
Let's take a look on my code fragment:

protected override void OnDayRender(TableCell cell, CalendarDay day)
{
if (day.IsSelectable)
{
cell.Text = string.Format("<a href=\"{0}.aspx\">{1}</a>", day.Date.ToString("dd-MM-yyyy"), day.DayNumberText);
}
}

It's clear, I just want to have a clickable numbers, but not with the navigate URLs like "_doPostBack..." etc etc. I want it to contain clear URLs, those are combinations of date and extension ".aspx". Why I needed it? Just to make a calendar control for viewing archive for some date.
That's almost all.

One moment that you would be interested in:
If you want to add some dynamic, JavaScript content to the cell, you can use it's Attributes collection. For example to make a background color yellow on mouseover, you would write something like this:
cell.Attributes["onmouseover"] = "this.style.backgroundColor='yellow'";
etc.

Have a good day!

 How to create ASP.NET form without action
Standard solution breaks the designer, I prefer the other way

Ok, first what I did is just opened site http://asp.net/learn, entered the ASP.NET section and found the video from "How Do I" series, which describes how to make URL rewriting.
Great video, my advice to you is to find a little free time and have a look at this too.
There is said that, if you want to make URL rewriting in your ASP.NET project, you just have to create a class, inherited from System.Web.IHttpModule, and implement it's methods. In the Init() method you have to assign event handler to the application event called BeginRequest. It's fired every time when the request is sent to the server.
If you didn't yet understand the logic, I want to explain: According to the request you can find the URL to which it's pointing, and then, if it's your wish, you can change that particular URL with something else. But don't think about it as it sounds from the start. Changing URL means that URL in the address bar remains unchanged, but request is sent to another URL, the one you provided for changing the old one. Great trick, yeah?
For example: consider you have a web site, and you have user profiles stored in your SQL DataBase or some other kind of source. Let's consider your site's domain name is http://mysite.com. Your task is to show the profiles of users. Of course you would not create so many ASP.NET pages as many users you have. Am I right? Then what would you do?
One of the ways is to create a page which will display user's information according to the provided parameters. Let's say you created a page UserProfile.aspx which expects user's login name written in the query string, like this: UserProfile.aspx?Login=someLogin. Easy logic.
In the code of the page you just check the value of Request.Querystring["Login"], which is of type string, and then you make a simple select statements from the data source.
Considering this, you can understand, that, if needed to display the profile of user with login "tengo", then you must enter the following URL in the address bar of your web browser:
http://mysite.com/UserProfile.aspx?Login=tengo
not a bad job.
But!
Why not to make it possible to access the profile of user with login "tengo" using the following URL:
http://mysite.com/Users/tengo.aspx
(just like my blog does).
It looks like you have to create a page named tengo.aspx but, using the feature of URL rewriting you can solve the problem very easy. In terms of URL rewriting, the request URL in this case is http://mysite.com/Users/tengo.aspx. and the second URL, using which you must change the requested URL, is the real, working URL, that is: UserProfile.aspx?Login=tengo.
And that means, that address in the address bar of the browser will be the first, and the request will be processed in the second one.

Ok, next step.

If you watched the video that I mentioned about, you would already know, that this approach has some not very comfortable results. One of them is: if you have any button or anything that makes the page submitting, that means, after clicking on that, user will see the URL that you so much tried to hide from the eyes of the user.
The same video, teaches us how to avoid this problem. You can just create your own class, inherited from System.Web.UI.HtmlControls.HtmlForm, and override it's RenderAttributes() method. Why you need that?
The reason that just opens you secret URL to the user is the "action" attribute of the form tag, that is contained on each ASP.NET page. If that attribute would not be there, everything would be just fine! I hope now you understood. After overriding the RenderAttributes() method you can just render all the attributes of the form except the one with a name "action". Great approach, I did try it on my own project, created the class of Form, registered that class in my ASP.NET page using <%@Register %> directive of ASP.NET, and then, just simply changed the tag <form> with my own tag name (the name of the class I had created).
Everything's fine, and you would think: that's all, the problem is solved.

Not so fast, please...

Yes, I changed the tag in my ASP.NET page, ran the project, saw the result. I was happy. Then, I just continued writing some other codes in the project and...
I was very surprised when I switched to the design view of the page and, what there happened is, there was nothing visible in the design view of the page. Everything disappeared, page was empty and a rectangle positioned in the left upper corner of the page was saying:

Error Creating Control - form1
Unable to cast object of type ‘System.Web.UI.Design.HTMLIntrinsicControlDesigner' to type ‘System.Web.UI.Design.ControlDesigner'

Now what? Designer is broken.
The first think I just thought, I would change the form tags back as it was from the beginning, continue the development, and then, before releasing it, I would change the tags as needed.
Not very comfortable solution (as for me).

Second solution:

Create a class inherited from System.Web.UI.HtmlTextWriter, override it's WriteAttribute methods, in the beginning of the method check if the name of attribute is "action", and if so just exit the method.
Then, create a class inherited from System.Web.UI.Page class. Override it's Render method, and make a rendering to your htmltextwriter class.
It was in a little amount of words, explained the solution. Now I'll explain all in details:

Every page in you project is a class inherited from the System.Web.UI.Page class. And of course, when rendering it to the browser as HTML, the rules contained in the Page class are used.
Now you understand, that if you'll have you own Page class, and write there the rendering rules, and then change your pages so as they inherit from your Page class, then every page will play with your rules.

Let's look at the code of my HTMLTextWriter class:

public class HTMLTextWriter : System.Web.UI.HtmlTextWriter
{
public HTMLTextWriter(System.Web.UI.HtmlTextWriter baseWriter) : base(baseWriter)
{
this.InnerWriter = baseWriter;
}

public override void WriteAttribute(string name, string value)
{
if (name.ToLower() == "action")
{
return;
}
base.WriteAttribute(name, value);
}

public override void WriteAttribute(string name, string value, bool fEncode)
{
if (name.ToLower() == "action")
{
return;
}
base.WriteAttribute(name, value, fEncode);
}
}

and here's the code of my Page class:

public class MyPage : System.Web.UI.Page
{
protected override void Render(System.Web.UI.HtmlTextWriter writer)
{
base.Render(new HTMLTextWriter(writer));
}
}

as you see, in the constructor of HTMLTextWriter class I'm saving the pointer to parameter baseWriter assigning it to the propery InnerWriter. InnerWriter is the writer that writes everything. I'm not interested what it was before this assignment. The fact is, I'm invoking Page class's Render method using a writer that must have everything rendered inside. And of course, code will be writing everything to this writer, because I saved the pointer to it.

Then, everything is very simply, overriding WriteAttribute methods, I write everything to exactly that writer, except the attribute named "action".

When done with this code, now you can access the code of your pages and change the inheritance of them. Like this (for my default page):

public partial class _Default : MyPage

let's try a designer... All's working fine!

Happy coding!