Dinesh's Blog ::::::: Being Compiled :::::::: ASP.NET 2.0

What should be my “Cookieless” value?

Mon, 24 Jul 2006 01:13:20 GMT

This is not a new issue, not a big issue but some stubborn customers of one my friends have put him into trouble. This is the case. What would happen to your session variables if customer has disabled the “cookie” in his browser? Since the default “Cookieless” mode is “UseCookies” (see the web.config file), new session id is created for every request. Because of that, the session variables set are not available for second request as new session id is created. There is no direct way to check whether the cookies are disabled unless checking it by storing some cookie and retrieving them. Though users are warned, some are not in position to enable cookie for various reasons (one common reason is, lack of knowledge).

So, what is the solution? When he asked from me, I told him that another way to do it, without using cookie to hold the session id, send it through URL, not manually, but setting it in web.config file; set “Cookieless” mode to “UseUri”. This works fine until you try to redirect user from one page to another page by using Response.Redirect. Remember, it inserts the session id for URL if it is a relative link but an absolute link.

What is the next solution? Making “Cookieless” mode to “AutoDetect”? I am not sure. I think it won’t create a solution because it a combination of above two settings. Best option is, if cookies are disable, warn customers and force them to enable it. But, , what is your opinion?

Chunk your view state

Thu, 13 Jul 2006 01:28:00 GMT

This might not be a new for you but I found that few ASP.Net developers still do not about this. As you all know, some proxies and firewalls refuse to let pages through if pages have hidden values greater than a certain size. This limitation might prevent your page seeing to the client if the page contains a view state that size is greater than the limitation. Since ASP.Net 2.0 allows you to chunk the view state, you can simply address this type of problems if exist.

All you have to do is, add “maxPageStateFieldLength” attribute to the page element with byte size value.

<system.web>
<pages maxPageStateFieldLength="50"/>
</system.web>

Once set, if the view state value is greater than the size set, several hidden fields will be created.

Why my XML file for AdRotator not so smart?

Tue, 21 Mar 2006 01:14:16 GMT

I just tried to add an xml file and made it as the source for AdRotator control but I found very strange thing with 2.0. I added a XML file an added the schema of AdRotator-Schedule_File. Strange, it didn’t add the Advertisement tag immediately but was available after little navigation between pages. Though it allows adding Ad element to the page, other tags such are ImageURL, Impression are not available. Why is that? Am I missing something. I had to add them manually, and then it worked fine. But what was the problem?

If you have done this without problem, appreciate if you share it with me.

Client still can’t scroll the disabled list box

Tue, 10 Jan 2006 01:09:40 GMT

One of the problems we had with ListBox in ASP.Net 1.1 is, it does not support scrolling while it is disabled. There are few workarounds for this like implementing client-side script, placing the ListBox inside the div. Yesterday I heard that now it is possible with 2.0. Guess what? It disappointed me. Still it is impossible though new properties such as “enable” for individual items.

First I thought that enabling the ListBox and disabling all the items in the box will produce the result I want but it shows nothing. If I enable couple of items in the box, they are shown but others. This is what I did.

//deselect and disable all

for (int x = 0; x < ListBox1.Items.Count; x++)

{

ListBox1.Items[x].Selected = false;

ListBox1.Items[x].Enabled = false;

}

//Enable and select items I want

//Expect to see all items in disable mode with selected ones

//It shows only the enabled one

ListBox1.Items[0].Selected = true;

ListBox1.Items[0].Enabled = true;

ListBox1.Items[4].Selected = true;

ListBox1.Items[3].Enabled = true;

ListBox1.Enabled = false;

Do you think that it is possible? If so, let me know please. Note that I do not want workarounds like mentioned above.

Make a use of Themes

Thu, 01 Sep 2005 01:35:41 GMT

I feel that the Theme facility in the asp.net 2.0 is something like "style sheet manager"? That’s how I thought. Actually this allows having separate style sheets, on controls and setting them dynamically. The setting can be set for application level, page level, container level and control level. I just tested this facility with following way.

Created a folder called "Theme" in the application.
Add a style sheet that has background color set to red.
Add a skin file (named as "Buttuns.skin") that has following line included
- <
asp:Button runat="server" BackColor="Black"ForeColor="White" />

Add two buttons for the default page and set the property of "EnableTheming" to "false" for one of the buttons

Add Theme="Theme" page directive to the page.

This will add the theme to the entire page but the one of buttons that "false" for "EnableTheming" property. Is this really cool? My involvement for graphical interface designing is very rare but feel that this will be really helpful for interface designers.

Auto code implement @ inheritance: Not working?

Tue, 05 Jul 2005 01:54:01 GMT

At the time I stepped into .net 1.1 from 1.0, one of changes I saw was code auto implanting at inheritance. For example, if the class “EmployeeCollection” is needed to be derived from “CollectionBase”, simply, we extend it by adding a “:” and typing the derived class. Once the word “CollectionBase” typed, a message appears and ask us to press tab to implement all methods to be written under “CollectionBase” class. Now, is it available in 2.0?

I found this just now and feel that a small problem exist with 2.0. When try to create a class by inheriting “CollectionBase” with same fashion, once the word “CollectionBase” is written, a small indicator is appeared under first letter of the derived class. When the indicator is clicked (either by mouse or {Shift+Alt+F10}), a menu that contains items related to the derived class is appeared that allows us create code for “CollectionBase” automatically.

The problem I faced is, though the menu item is clicked, it will not create methods. Then I tested the same with some interfaces, and it worked fine.

As still I am beginner for .net 2.0, I think the logic behind is unknown to me. Can I have advice on this from u experts?

Validation Group

Mon, 04 Jul 2005 02:05:10 GMT

By implementing ValidationGroup for ASP.Net controls, VS team has done a wonderful job. This allows us to have a web page with separate section and validate them separately at submit. For example, assume that we have a login page (of course, you do not need to worry about creating login page now) that has two login panes, one for customers and one for administrators that will use emails and login id respectively. By setting like below, we can easily validate the section we need.

RequiredFieldValidatorCustomerEmail.ValidationGroup = "Customer";

RequiredFieldValidatorCustomerEmail.ControlToValidate = "TextBoxCustomerEmail";

RequiredFieldValidatorCustomerPassword.ValidationGroup = "Customer";

RequiredFieldValidatorCustomerPassword.ControlToValidate = "TextBoxCustomerPassword";

ButtonCutomerLogin.ValidationGroup = "Customer";

RequiredFieldValidatorAdminLoginId.ValidationGroup = "Admin";

RequiredFieldValidatorAdminLoginId.ControlToValidate = "TextBoxAdminLoginId";

RequiredFieldValidatorAdminPassword.ValidationGroup = "Admin";

RequiredFieldValidatorAdminPassword.ControlToValidate = "TextBoxAdminPassword";

ButtonAdminLogIn.ValidationGroup = "Admin";

If no ValidationGroup is specified, it will behave just as 1.1.

PostBackURL Property of ASP.NET 2.0

Tue, 07 Jun 2005 01:44:37 GMT

If I need to re-direct the user from one page to another page when submit, with ASP.NET 1.1, always used "Response.Redirect" in button click event. The re-direction can be done at client side if no processes need to be executed at server side. But in most cases, we need to process something (usually what user entered) before re-directing. One of the new properties come with version 2.0 is "PostBackURL" that supports us to do the same thing easily with some advantages.

By setting "PostBackURL" of the submit button to the page we need, the page can be easily re-directed.

//page load of "Default.aspx"
protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      Button1.PostBackUrl = "Default2.aspx";
   }
}

Once we set like above, user will be redirected to the page (Default2.aspx) when submit the default page by clicking the Button1. The advantage of this is, we can easily access the the controls in Source Page (Default.aspx) from Target Page (Default2.aspx) by using "PreviousPage" property of target page.

//code in the Default2.aspx
if (PreviousPage != null)
   {
   //looking for TextBox1 of Default.aspx page text
   TextBox textBox = (TextBox)PreviousPage.FindControl("TextBox1");
   Response.Write(textBox.Text);
   }

Can I access all public properties declared in Default.aspx through Default2.aspx? Yes, this can be done. The 2.0 allows to add an new page directive that is called PreviousPageType. Once this is set to (this page directive contains an attribute called VirtualPath that is used set the "SourcePage".) the page that we expect to use as source page, all public properties declared in source page can be accessed through target page.

//property declared in Default.aspx
public string TestProperty { get { return "This is the value of TestProperty of Default.aspx";} }

if page directive is set in Default2.aspx by pointing "Default.aspx" as source

<%@ PreviousPageType VirtualPath="~/Default.aspx" %>

And the Default.aspx is redirected to the Target (Default2.aspx), the property can be accessed at Default2.aspx by;
PreviousPage.TestProperty

One thing I noticed is, when the redirection occurs, the source page "Page_Load" and "Button Click" events are ONLY fired when "PreviousPage" property is accessed. If the target page is not accessed the source page by using "PreviousPage" property, the above events in source page are not fired. I am not quite sure why this type of behavior is set. I accidentally came across this behavior when I try access a Session variable that set in Button_Click at source page. If the "PreviuosPage" is not accessed in target page, session variable contains the default value but contains new value if the property is called.

Here is a test code in source page
protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      Session["TestSessionValue"] = "This is default value";
      Button1.PostBackUrl = "Default2.aspx";
   }
}

Button click event in the source page
protected void Button1_Click(object sender, EventArgs e)
{
Session["TestSessionValue"] = "Value is set by Default.aspx.Button1.Click event";
}

Code in the target page
protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      Response.Write(Session["TestSessionValue"].ToString());
      Response.Write("<br>");

      if (PreviousPage != null)
      {
         Response.Write(Session["TestSessionValue"].ToString());
      }
   }

}

The output will be;
This is default value
Value is set by Default.aspx.Button1.Click event

Anyway, this is really helpful. I just started exploring the 2.0 and lot to dig up.