I have a Default.aspx page and I am using a usercontrol in it. On some condition in usercontrol.cs I have to invoke a function present in Default.aspx.cs page (i.e parent page of user control). Please help and tell me the way to do this task.
You have to cast the Page property to the actual type:
var def = this.Page as _Default;
if(def != null)
{
def.FunctionName();
}
the method must be public:
public partial class _Default : System.Web.UI.Page
{
public void FunctionName()
{
}
}
But note that this is not best-practise since you are hard-linking the UserControl with a Page. Normally one purpose of a UserControl is reusability. Not anymore here. The best way to communicate from a UserControl with it's page is using a custom event which can be handled by the page.
Mastering Page-UserControl Communication - event driven communication
Add an event to the user control:
public event EventHandler SpecialCondition;
Raise this event inside your user control when the condition is met:
private void RaiseSpecialCondition()
{
if (SpecialCondition != null) // If nobody subscribed to the event, it will be null.
SpecialCondition(this, EventArgs.Empty);
}
Then in your page containing the user control, listen for the event:
public partial class _Default : System.Web.UI.Page
{
public void Page_OnLoad(object sender, EventArgs e)
{
this.UserControl1.OnSpecialCondition += HandleSpecialCondition;
}
public void HandleSpecialCondition(object sender, EventArgs e)
{
// Your handler here.
}
}
You can change the EventArgs to something more useful to pass values around, if required.
parent.aspx.cs
public void DisplayMsg(string message)
{
if (message == "" || message == null) message = "Default Message";
Response.Write(message);
}
To Call function of parent Page from user control use the following:
UserControl.ascx.cs
this.Page.GetType().InvokeMember("DisplayMsg", System.Reflection.BindingFlags.InvokeMethod, null, this.Page, new object[] { "My Message" });
This works fine for me..
Try this
MyAspxClassName aspxobj= new MyUserControlClassName();
aspxobj.YourMethod(param);
Related
There is parent user control, as seen below.
<%# Control Language="C#" AutoEventWireup="true" CodeFile="TestUserControl.ascx.cs" Inherits="TestUserControl" %>
<%# Register Src="~/UserControls/ChildUserControl.ascx" TagName="ChildUserControl" TagPrefix="FLI" %>
<div>
<FLI:ChildUserControl ID="child1" runat="server"/>
</div>
The child usecontrol has pulic property MatchDescription, which is set in the Page_Load of the parent control. I want to cache multiple versions of the child control, based on the MatchDescription property.
Problem is, the MatchDescription property cant be set in Page_Load, as the cached copy of the child control is used once its available.
How can i fix this problem?
Thanks!
It looks like using GetVaryByCustomString is the way to go here. My proof of concept consisted of the following:
WebUserControl.ascx: the test control. It has a single public property MatchDescription.
Global.asax: to override the GetVaryByCustomString method.
WebForm.aspx: a simple form to host the control.
WebUserControl.ascx
Add the following to the markup on the control:
<%# OutputCache Duration="120" VaryByParam="none" VaryByCustom="MatchDescription" %>
This specifies the duration (in seconds) to cache the control and VaryByCustom="MatchDescription" specifies the name of the parameter we will be caching on.
WebUserControl.ascx.cs
public partial class WebUserControl1 : System.Web.UI.UserControl
{
public string MatchDescription { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
object description = this.Context.Application["MatchDescription"];
if (description != null)
{
this.MatchDescription = description.ToString();
}
else
{
this.MatchDescription = "Not set";
}
Label1.Text = "Match description: " + this.MatchDescription;
}
}
This will check for the existance of the MatchDescription value. Because of the way the code in the parent page works, you should never see "Not set", though in your implementation it may be useful just in case the value is not set.
Global.asax
Add a Global.asax file to your project and add in the following method:
public override string GetVaryByCustomString(HttpContext context, string custom)
{
if (custom == "MatchDescription")
{
object description = context.Application["MatchDescription"];
if (description != null)
{
return description.ToString();
}
}
return base.GetVaryByCustomString(context, custom);
}
This is the bit that checks for the MatchDescription associated with the cached control. If it is not found the control will be created as normal. context.Application is used because we need a way to communicate the description value between the parent page, the user control and the global.asax file.
WebForm.aspx.cs
public partial class WebForm : System.Web.UI.Page
{
private static string[] _descriptions = new string[]
{
"Description 1",
"Description 2",
"Description 3",
"Description 4"
};
protected override void OnPreInit(EventArgs e)
{
//Simulate service call.
string matchDescription = _descriptions[new Random().Next(0, 4)];
//Store description.
this.Context.Application["MatchDescription"] = matchDescription;
base.OnPreInit(e);
}
protected void Page_Load(object sender, EventArgs e)
{
var control = LoadControl("WebUserControl.ascx") as PartialCachingControl;
this.Form.Controls.Add(control);
//Indicate whether the control was cached.
if (control != null)
{
if (control.CachedControl == null)
{
Label1.Text = "Control was cached";
}
else
{
Label1.Text = "Control was not cached";
}
}
}
}
Note that in this code I am making/simulating the service call in the OnPreInit method. This is necessary as it occurs in the page lifecycle before the GetVaryByCustomString method.
Keep in mind that if a control has been cached, accessing it in the Page_Load method, for example, will require code of this form:
if (control is PartialCachingControl &&
((PartialCachingControl)control).CachedControl =!= null)
{
WebUserControl1 userControl = (WebUserControl1)((PartialCachingControl)control).CachedControl;
}
References:
My answer was inspired by: Any way to clear/flush/remove OutputCache?
I found the Pre_Init hint in this question:
Output Caching - GetVaryByCustomString based on value set in PageLoad()
This KB article discusses why the PartialCachingControl.CachedControl property can always return null:
http://support.microsoft.com/kb/837000
I want to check Session in some pages. To do this I am adding the page names which I want to check inside web.config as a appsetting key.
I want to use httpHandler with firing an event after it finds the session is empty or something else.
If I create httpHandler as a dll(another project) and add to a web site, can handler fire an event and web site capture it inside a web page?
What you can do is this:
Your HttpHandler puts a value in the HttpContext.Current.Items collection telling if there was Session or not. Something like
HttpContext.Current.Items.Add("SessionWasThere") = true;
You create a BasePage that checks that value in the Page_Load event and raises a new event telling so:
public abstract class BasePage : Page {
public event EventHandler NoSession;
protected override void OnLoad(EventArgs e){
var sessionWasThere = (bool)HttpContext.Current.Items.Add("SessionWasThere");
if(!sessionWasThere && NoSession != null)
NoSession(this, EventArgs.Empty);
}
}
In your page, you suscribe to that event:
public class MyPage : BasePage{
protected override void OnInit(){
NoSession += Page_NoSession;
}
private void Page_NoSession(object sender, EventArgs e) {
//...
}
}
I have a user control on the master page and I would like to pass in a value into that user control from the subpage, how would I be able to pass the values?
This control is in the master page
<%# Register TagPrefix="test" TagName="Data" Src="controls/TEST.ascx" %>
This code variable is within the user control
public partial class Controls_TEST : System.Web.UI.UserControl
{
private string _Title;
public string Title
{
get { return _Title; }
set { _Title = value; }
}
}
Code within the subpage
public partial class sub_page : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
Controls_Test m = LoadControl("~/Controls/TEST.ascx");
m.Title = "TEST";
}
}
Note the sample code within subpage does not work because it cannot find that user control within the subpage.
I've tried Page.Master.FindControl and it also does not work for me. PLease help.
Use properties to communicate from your Page to your MasterPage and use properties to communicate from your MasterPage to the UserControl.
To get a reference to the control in your MasterPage you should provide a public property that returns it:
For example(in MasterPage):
public Controls_Test MyControl
{
get
{
return Controls_TEST1;
}
}
And you can call this property from one of your ContentPages in this way(f.e. if your master's type is named "SiteMaster"):
protected void Page_Load(object sender, EventArgs e)
{
((SiteMaster)Page.Master).MyControl.Title = "TEST";
}
As a rule of thumb: the more you encapsulate your controls, the more robust ,failsafe, maintanable and extendable your code will be.
Hence it would be better to provide only access to the Title rather than to the whole UserControl.
In MasterPage:
public String Title
{
get
{
return Controls_TEST1.Title;
}
set
{
Controls_TEST1.Title = value;
}
}
In the ContentPage:
((SiteMaster)Page.Master).Title = "TEST";
On this way you could change the logic and controls in your UserControl and MasterPage without having problems in your pages that already have accessed the UserControl directly.
I've run into a weird problem while developing a control. I've registered a handler for Page.InitComplete event from the control, but the handler is not executed. I need the handler to be executed exactly on InitComplete event, because I depend on complex application architecture.
My code looks like this (This code is placed inside my control class):
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
this.Page.InitComplete += (sender, args) => OnInitComplete(args);
}
However OnInitComplete is never entered.
If it is somehow possible I would like to find the way to register my handler to Page.InitComplete event without using my own events & weird hacks.
Apart from that I'm curious about the reason of this behaviour.
I'm sorry - my fault. The problem was in custom PageBase class :
protected override void OnInitComplete(EventArgs e)
{
if (!String.IsNullOrEmpty(FormAction) && FormActionInitComplete != null)
{
FormActionInitComplete(FormActionSender, FormAction, FormActionValue);
}
}
The Page.OnInitComplete method is implemented in the following way :
protected virtual void OnInitComplete(EventArgs e) {
EventHandler handler = (EventHandler)Events[EventInitComplete];
if (handler != null) {
handler(this, e);
}
}
and in the overriden method of the PageBase there was no call of the base.OnInitComplete method - that is why the event was not raised.
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();
}