Is there a way to force methods to be accessible only during certain events during the page life cycle. For example, I have a extension to System.Web.UI.Page that adds a PrependTitle method.
I also have a masterpage that embeds another masterpage. The first masterpage sets the base title (Google), the next masterpage prepends the title (Calendar), and a page also prepends the title (21 May 2011).
The result should be:
21 May 2011 :: Calendar :: Google
And this is the case when the PrependTitle is run during the Page_Init event. However, when the method is run during Page_Load the following the results:
Google
So, that brings me to the question: How can it be enforced that a method only be accessible during specified life cycle events?
// The Method Mentioned
public static class PageExtensions
{
public static void PrependTitle(this Page page, string newTitle)
{
page.Title = newTitle + " " + Global.TITLE_DELIMITER + " " + page.Title;
}
}
I think this can be done similar to the following. The general idea is declare the method as private, declare the ones that should have access to it as sealed
class AppsBasePage : Page
{
abstract void PrependTitle(string title);
}
class PageWithTitlePrepended : AppsBasePage
{
private void PrependTitle(string title)
{
Title = String.Format("{0} {1} {2}", newTitle, Global.TITLE_DELIMITER, Title);
}
protected sealed override void Page_Init(object sender, EventArgs e)
{
PrependTitle("This is a title")
}
}
class ActualPageInApp: PageWithTitlePrepended
{
override void Page_Load(object s, EventArgs e)
{
// can't access PrependTitle here
}
}
This solves your question in bold, but I'm not convinced this situation is what is causing your problem with PrependTitle specifically. I think more code / context would be needed to solve your actual problem
If you want to brute force ensure that the method is being called from Init, you can inspect the call stack. Something like this:
public static bool CalledFromInit()
{
//Grab the current Stack Trace and loop through each frame
foreach(var callFrame in new StackTrace().GetFrames())
{
//Get the method in which the frame is executing
var method = callFrame.GetMethod();
//Check if the method is Control.OnInit (or any other method you want to test for)
if(method.DeclaringType == typeof(Control) && method.Name == "OnInit")
//If so, return right away
return true;
}
//Otherwise, we didn't find the method in the callstack
return false;
}
Then you would use it like:
public static void PrependTitle(this Page page, string newTitle)
{
//If we aren't called from Init, do something
if (!CalledFromInit())
{
//We could either return to silently ignore the problem
return;
//Or we could throw an exception to let the developer know they
// did something wrong
throw new ApplicationException("Invalid call to PrependTitle");
}
//Do the normally processing
page.Title = newTitle + " " + Global.TITLE_DELIMITER + " " + page.Title;
}
However, I'd caution that the stack trace isn't the most reliable thing. In release, code could get optimized such that the Control.OnInit method is inlined so your code wouldn't be able to see it in the call stack. You could wrap this check in an #if DEBUG block so it only executes during development. Depending on your use case, it might be good enough to catch this problem while in DEBUG and not bother doing the check in RELEASE. But that's up to you.
Another option...building on Tommy Hinrichs answer, if all your pages inherit from a base class, you'll be able to do it a bit more reliably. I'd suggest something like this:
public abstract class BasePage : Page
{
private bool _executingInit;
protected internal override void OnPreInit(EventArgs e)
{
_executingInit = true;
base.OnPreInit(e);
}
protected internal override void OnInitComplete(EventArgs e)
{
base.OnInitComplete(e);
_executingInit = true;
}
public void PrependTitle(string newTitle)
{
if (!_executingInit)
throw new ApplicationException("Invalid call to PrependTitle.");
Title = newTitle + " " + Global.TITLE_DELIMITER + " " + Title;
}
}
That way, PrependTitle will throw an exception unless it's called between PreInit and InitComplete (which sounds like exactly what you want).
As one last option, you could be sneaky and use reflection to access the Control.ControlState property (which is a confusing name because it's not related to Control State - the thing similar to View State). That property tracks the Control as it goes throw its lifecycle - and it has the following values:
internal enum ControlState
{
Constructed,
FrameworkInitialized,
ChildrenInitialized,
Initialized,
ViewStateLoaded,
Loaded,
PreRendered
}
You'll notice that Enum is internal. So is the Control.ControlState property. But with Reflection, you could use that - and you could even use it from an extension method that is external to the Page.
Hope one of those ways will work for you!
Your best bet is probably to use the Handles Keyword to attach the method to the event.
You might have to create a subclass of System.Web.UI.Page to ensure this is enforced.
It seems that the issue is in the prependTitle method, it should append the text to the page title not replace it.
Just call the PrependTitle method in the page_load of each mashterpage and page and append the text to the title.
Related
I have a problem when accessing httpcontext.current value at application_start method.
There is a lots of discussions about this topic.
But I want to share my business logic and I need some advice how to handle problem.
Let's look at this business logic together step by step
1-I want to design "custom object" which has "static global List" property and any user can add "LogObj" object to this list whereever actions occured.
public class MyLog
{
public static void List<LogObj> LogObjList {get;set;}
static MyLog()
{
LogObjList = new List<LogObj>();
}
}
2- If I have a "System.Timers.Timer" object which checks the "static global List" every X milliseconds and performs some action which defined in the code
public static init(){
System.Timers.Timer t = new System.Timers.Timer();
t.Elapsed += T_Elapsed;
t.Interval = 3000;
t.Start();
}
private void T_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
//perform some code.
var s = HttpContext.Current.Session["test"];
var logObj = MyLog.LogObjList[0] + s;
//save as text file ...
}
3- If I start init() method in application_start event at global.asax I get this error "object reference ..." where the line of "..HttpContext.Current.Session" started.
So
If I do not want to access any httpcontext.current's properties I have no problem at this situation.
But If I need to access any properties of httpcontext.current at Timer_Elapsed event I have problem about it.
So I need your advice or alternative way to making my algorithm.
Thank you
Newbie here, I need help with a website I'm creating.
I have a class that does some analysis on some text that is input by the user, the class then finds an appropriate answer and sends it back to the textbox. (in theory)
Problem is I don't know how I can control and access the textbox on the default.aspx page from a class, all I get is "object reference is required non static field".
I made the textbox public in the designer file yet still no joy. :(
I've also read this: How can I access the controls on my ASP.NET page from a class within the solution? , which I think is along the lines of what I'm trying to achieve but I need clarification/step by step on how to achieve this.
Hope someone can point me in the right direction.
Many thanks,
Kal
This is the code I have added to the designer.cs file:
public global::System.Web.UI.WebControls.TextBox TextBox3;
public string MyTextBoxText
{
get
{
return TextBox3.Text;
}
set
{
TextBox3.Text = value;
}
}
This is the class method i have created:
public static cleanseMe(string input)
{
string utterance = input;
string cleansedUtt = Regex.Replace(utterance, #"[!]|[.]|[?]|[,]|[']", "");
WebApplication1._Default.TextBox3.text = cleansedUtt;
}
I could just return the cleansedUtt string i know, but is it possible for me to just append this string to the said textbox from this method, within this class?
I also tried it this way, i wrote a class that takes in the name of the textbox and string to append to that textbox. it works BUT only on the default.aspx page and does not recognise the textbox names within the difference classes. The code is as follows:
public class formControl
{
public static void ModifyText(TextBox textBox, string appendthis)
{
textBox.Text += appendthis + "\r\n";
}
I would suggest you that do not access the Page Controls like TextBox in your class. It will be more useful and a good practice that whatever functionality your class does, convert them into function which accept the parameters and returns some value and then on the basis of that value you can set the controls value.
So now you have reusable function that you can use from any of the page you want. You do not need to write it for every textbox.
Here I am giving you a simple example
public class Test
{
public bool IsValid(string value)
{
// Your logic
return true;
}
}
Now you can use it simple on your page like this
Test objTest = new Test();
bool result=objTest.IsValid(TextBox1.Text);
if(result)
{
TextBox1.Text="Everything is correct";
}
else
{
TextBox1.Text="Something went wrong";
}
If you have your class in the same project (Web Project) the following will work:
public class Test
{
public Test()
{
//
// TODO: Add constructor logic here
//
}
public static void ValidateTextBox(System.Web.UI.WebControls.TextBox txt)
{
//validation logic here
if (txt != null)
txt.Text = "Modified from class";
}
}
You can use this from your webform like this:
protected void Page_Load(object sender, EventArgs e)
{
Test.ValidateTextBox(this.txt);
}
If your class is in a different (class project), you would need to add a reference to System.Web to your project.
I've 2 user controls named UCCreateProfile.ascx (used for creating/editing profile data) and UCProfileList.ascx (used to display profile data in GridView). Now whenever a new profile created I want to update my UCProfileList control to show new entry.
The best solution against above problem I've to go for Observer Pattern. In my case UCCreatedProfile is a Subject/Observable and UCProfileList is a Observer and as per pattern definition when observer initialized it knows who is my Subject/Observable and add itself into Subject/Observable list. So whenever a change occurred in Subject/Observable it will be notified.
This pattern best fit my requirements but I'm getting few problems to implement this describe as follows.
I'm working under CMS (Umbraco) and I don't have any physical container page (.aspx). What I've to do is find UCCreateProfile (Subject/Observable) in UCProfileList (Observer) onLoad event using following code.
private Control FindCreateProfileControl()
{
Control control = null;
Control frm = GetFormInstance();
control = GetControlRecursive(frm.Controls);
return control;
}
where GetFormInstance() method is
private Control GetFormInstance()
{
Control ctrl = this.Parent;
while (true)
{
ctrl = ctrl.Parent;
if (ctrl is HtmlForm)
{
break;
}
}
return ctrl;
}
and GetControlRecursive() method is
private Control GetControlRecursive(ControlCollection ctrls)
{
Control result = null;
foreach (Control item in ctrls)
{
if (result != null) break;
if (item is UCCreateProfile)
{
result = item;
return result;
}
if (item.Controls != null)
result = GetControlRecursive(item.Controls);
}
return result;
}
this way I can find the UCCreateProfile (Subject/Observable) user control in UCProfileList (Observer) but the way to find out the (Subject/Observable) is not so fast. As you can see I need to loop through all controls and first find the HtmlForm control and then loop through all child controls under HtmlForm control and find the appropriate control we're looking for.
Secondly, placement of the user controls in container if very important my code will only work if UCCreatedProfile.ascx (Subject/Observable) placed before UCProfileList.ascx (Observer) because this way UCCreateProfile will load first and find in UCProfileList. But if someone changed the position of these 2 controls my code will not work.
So to get rid of these problems I need some solution which works faster and independent of the position of the controls.
I've figured out some solution as described below. Please do let me know if it is a good way of doing this. If there is an alternative, please let me know.
I've a session level variable (a dictionary with Dictionary<ISubject, List<Observer>>) . No matter which user control initialized/loaded first, User Control will add itself into this dictionary.
If Subject/Observable added first, the corresponding observers will be found in this dictionary.
If Observer added first it will added to the dictionary with a null entry. When the Subject added, the association is made.
Regards,
/Rizwan
The Observer pattern is best implemented in .NET via events and delegates. If you use events and delegates, the Dictionary you mention becomes completely unnecessary. See for example this code below (only important pieces shown):
public partial class UserProfile : System.Web.UI.UserControl
{
//This is the event handler for when a user is updated on the UserProfile Control
public event EventHandler<UserUpdatedEventArgs> UserUpdated;
protected void btnUpdate_Click(object sender, EventArgs e)
{
//Do whatever you need above and then see who's subscribed to this event
var userUpdated = UserUpdated;
if (userUpdated != null)
{
//Initialize UserUpdatedEventArgs as you want. You can, for example,
//pass a "User" object if you have one
userUpdated(this,new UserUpdatedEventArgs({....}));
}
}
}
public class UserUpdatedEventArgs : EventArgs
{
public User UserUpdated {get;set;}
public UserUpdatedEventArgs (User u)
{
UserUpdated=u;
}
}
Now subscribing to the UserUpdated event from the UserProfile control on the UserListControl is as easy as this:
public partial class UserList : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
//Find the UserProfile control in the page. It seems that you already have a
//recursive function that finds it. I wouldn't do that but that's for another topic...
UserProfile up = this.Parent.FindControl("UserProfile1") as UserProfile;
if(up!=null)
//Register for the event
up.UserUpdated += new EventHandler<UserUpdatedEventArgs>(up_UserUpdated);
}
//This will be called automatically every time a user is updated on the UserProfile control
protected void up_UserUpdated(object sender, UserUpdatedEventArgs e)
{
User u = e.UserUpdated;
//Do something with u...
}
}
I need the following functionality in my method: if the method is called before OnLoad event of ASP.NET life cycle throw an exception else continue execution of the method.
I was thinking of something like this:
if (Page.LifeCycleState < LifeCycleState.OnLoad) {
throw new InvalidPageStateException();
}
Is it possible to retrieve the state of ASP.NET page life cycle?
One approach would be to use a Basepage that you always use in your site. This would contain a variable called PageLoadComplete, which you would set at the end of your PageLoad event. Then you could check the state of this variable from within your method.
public abstract class BasePage : System.Web.UI.Page
{
public bool PageLoadComplete { get; private set; }
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
PageLoadComplete = true;
}
}
If you want to access the variable from code external to your page such as a UserControl, you would have to make it public and cast your page as BasePage.
public partial class MyUserControl : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
BasePage basePage = this.Page as BasePage;
if (basePage != null && !basePage.PageLoadComplete)
{
throw new InvalidPageStateException();
}
}
}
There is property in a realization of System.Web.UI.Control class(realization):
internal ControlState ControlState {
get { return _controlState; }
set { _controlState = value; }
}
Where ControlState is enum that contains members such as: Initialized, ViewStateLoaded, Loaded etc. here declaration
But as you can see this property is internal. So only way to get control state is proposed by Daniel Dyson.
You maybe able to find what you are looking for, by looking at the CurrentHandler and PreviousHandler properties of the current HttpContext.
if the method is called before OnLoad event of ASP.NET life cycle
throw an exception else continue execution of the method.
It is not clear which Onload event is meant, nor where the "method" resides. Is it the Page's Onload or a Control's OnLoad? Is it a Page's "method" or a Control's "method"?
Anyway, one can store sort of flag in the Context.Items Dictionary, which all controls (including Page) have access to during a request. This eliminates the need to use a general base page like suggested obove.
In the OnLoad method (no matter whether it is a Page's OnLoad or a Control's OnLoad):
Context.Items[UniqueID] = this;
In the "method":
if (Context.Items[UniqueID] != null)
{
throw new InvalidPageStateException();
}
In my Asp.Net project I wanna use Property Auto-wiring, e.g. for my ILogger. Basically I placed it as Property into class where I need to use it. Like below.
public class UserControlBase : UserControl
{
public ILogger CLogger { get; set; }
....
}
public partial class IPTracking : UserControlBase
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
string ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
//it works
ILogger logger = ObjectFactory.GetInstance<ILogger>();
logger.LogInfo(string.Format("Client IP: {0}", ip));
//it does not work
CLogger.LogInfo(string.Format("Client IP: {0}", ip));
}
}
}
However when calling in inherited control, logger is null. I checked the container and it'a definitely set as above implementation shows. Below is setting which is called from Global.asax.
public static void SetupForIoC()
{
Debug.WriteLine("SetupForIoC");
ObjectFactory.Initialize(x =>
{
x.FillAllPropertiesOfType<ILogger>().Use<EntLibLogger>();
});
Debug.WriteLine(ObjectFactory.WhatDoIHave());
}
Thanks for any advice, tip? X.
Update:
- I didnt mentioned before, but its Asp.Net webforms 3.5.
- I can't see what I am missing. I guess it could be because the injection gets involved later in process and didnt get set in requested class.
Link to desc. of usage: http://structuremap.github.com/structuremap/ConstructorAndSetterInjection.htm#section7
Give something like this a shot.
FillAllPropertiesOfType<ILogger>().AlwaysUnique().Use(s => s.ParentType == null ? new Log4NetLogger(s.BuildStack.Current.ConcreteType) : new Log4NetLogger((s.ParentType)));
Check out another StackOverflow answer I have which discusses using StructureMap to auto wire loggers.
Where do you actually set the CLogger property on the user control? Also, if you wanted to use one logger within the page, you could have the User cotnrol do:
public ILogger CLogger
{
get
{
if (this.Page is PageBase)
return ((PageBase)this.Page).Logger;
else
return null;
}
}