I've looked around and didn't find anuthing similar, what I'm looking for is a way to disable or stop whatever action that make the page post back on the page_load method according to some validation
example:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Page.IsPostBack Then
'Validate here and stop the action
End If
End Sub
I've already tried to end the request but in this way I can't tell the user whats going on
If the page fails validation, then the whole idea that no post back WILL occur! So you as a general rule don't check in the post back for a validation that supposed to not allow the post back!!!
If validation and the validators are working correctly, then no post back can and should occur. Now if you want code behind to do some extra logic and processing and some extra testing?
The of course you allow the post back, and thus now in that button event code stub, or say dropdown list or whatever event code stub is being triggered? It is in THAT code that you can add additional validation.
So you might have a VERY nice regex validator that requires the user MUST enter a legal formatted email address. They then hit ok, and say you then run some code to check if the email is on-file, and at that point your code behind can:
Display a message on the screen, or even trigger a toast message (client side). Note that you CAN trigger nice toast message or client side script if that is the VERY last thing your code behind does, and this works rather well.
So yes, one can and will often have a mix between some validators on the page, and THEN some additional code "behind" that does and will run as a result of the post back having been allowed.
But, if validators (client side) are working, then you not have any post back to run, and thus you can't check anything at all anyway. If the validators are working correct, then no post back should occur at all.
However, as noted, if you need to write some additional logic for that button or control event? Then you let the post back occur, run that additonal logic, and display a message, or toast message or do whatever based on that input, and then the page will rendered again.
Related
I have an asp:Button that fires a code behind function on the OnClick event. In that OnClick event several things happen, and among those things I do a check in the database for if I need to ask the user a yes or no question. For that I need a message box. First I did it like this:
protected void MyButton_Onclick(object sender, EventArgs e)
{
// lots of stuff happening
bool iNeedToAskTheUser = INeedToAskTheUser(stuff);
if (iNeedToAskTheUser)
{
DialogResult result = MessageBox.Show("Do you want to fix all objects?", "Fix objects", MessageBoxButtons.YesNo);
if (result == DialogResult.Yes) // do stuff
}
// some other stuff
}
This works fine locally but not when deployed, so I figure I would need to use ScriptManager.RegisterStartupScript instead. I could just add javascript on the ASPX page that fires up a dialog and saves the response in a hidden control that I can then look at, but I don't want to fire up the dialog unless I have to, which I check for before I do the DialogResult in the code above. So I can't do that immediately when the user clicks the button.
Is there any way I can use ScriptManager.RegisterStartupScript in "the middle" of my _OnClick code so that I can choose whether or not to actually show the button, and then also know if the user clicked yes or no, (preferably) without doing a postback?
I've been thinking and testing two different solutions:
Use ScriptManager.RegisterStartupScript in code behind to fire a JavaScript confirm function on the ASPX page. The JavaScript function would set a value in a hidden control depending on if the user answered yes or no and then my code behind stuff would check the value of that hidden field and act upon that. The problem with that is that once ScriptManager.RegisterStartupScript fires it doesn't wait for the JavaScript function to "finish", ie wait for the user to reply to the confirm(). So the value in the hidden control will always be empty because the code behind gets to the check of that control before the user has a chance to respond to the confirm(). So that's a no go.
Use ScriptManager.RegisterStartupScript in code behind to open up a new ASPX page that asks the user the question and then does all the work in response to the user's answer in that page. The problem then is to pass the object that the new ASPX page needs to do work on in response to the user's response.
I'm sure there are great solutions using Ajax or jQuery but this is a fairly simple function that shouldn't take too long to develop, so that is kind of out of scope for this.
Instead I'll go with a solution where I know what the user will respond to the question before they click the button. (While silently muttering under my breath: "It's 2019 and there's no good way to fire up a yes/no dialog from code behind in a .Net web project...". I need to get back to not working with web).
I'm new to web development, and I'm currently using ASP.net. I wonder what would I need to do to let the browser wait for 3 seconds so my users can read the text "Customer Successfully Added" before turning to another page? I have attached my code as follows.
Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click
Dim db As New DatabaseClass
db.addProfile(txtLN.Text, txtFN.Text, txtUsername.Text, txtPassword.Text, txtAddress.Text, txtZip.Text, txtPhone.Text, txtEmail.Text)
lblMessage.Text = "Customer Successfully Added"
End Sub
In addition, I'm not sure how to utilize MSDN. For me, its information overload, I'm wondering how to go about finding the solution on MSDN so i would be able to solve my problems in the future. Thank you!
You can't do it in the code behind of the page because of how asp.net works - the label text would not update until after the timeout occurred if you did it in the code-behind.
The server-side processing spits all the html back to the browser only after it has completely processed any server-side code unless you're using Ajax. Since you're new, I won't even bother going into how to do it with Ajax as there is a MUCH simpler option for accomplishing what you want.
A simple method to accomplish what you're looking for would be to have a simple HTML page that just has a message that says "Customer successfully added" and use javascript (client-side code) to pause and then redirect using the Javascript "SetTimeout" function.
There's an example here: http://www.bloggingdeveloper.com/post/JavaScript-Url-Redirect-with-Delay.aspx
The logic flow wshould work like this:
The original page should add the record (in code-behind) then redirect to this simple html page (in code-behind). The html page should have the "Customer Added" message and use the SetTimeout and Redirect to go to whatever page you want the user to see after viewing the message.
For stuff like this you need the code to run client side rather than on the server. The easiest way to do this is to return some javascript with your page (in the .aspx part rather than the code behind)
Take a look here for an idea of what to do :)
The page is displayed for a few seconds and then the javascript triggers a redirect to a url of your choosing. Just add something like this into your html.
You can emit javascript to redirect to the other page, using the setTimeout function.
This is best accomplished using the ScriptManager to register any javascript on the page.
I know that ASP.NET controls such as the button have the postback event model. And checking whether the page.IsValid is dependent on events and postback in order for the validation to kick in.
But what if I have a button using regular HTML inside my .aspx (and I don't want to use the asp.net button...please do not ask me why) yet still want to take advantage of calling Page.IsValid?
For example, lets say my .aspx page has 2 buttons:
<asp:ImageButton runat="server" ID="cmdPlaceOrder" OnClick="cmdPlaceOrder_Click" ImageUrl="images/someButton.gif" />
and that was there in the page, someone else had created that a while back. In the cmdPlaceOrder we check for Page.IsValid:
protected void cmdPlaceOrder_Click(object sender, EventArgs args)
{
if (!IsValid)
return;
... rest of logic
}
That's standard. Now what if I add a non-ASP.NET button like this in the .aspx page, used to place the order (but for a different kind of order seperate from the existing place order button above):
<img src="images/buttonPayGoogleCheckout.gif" alt="Pay with Google"/>
So on click of the hyperlink, the page posts back to itself (same url). I check the url for a querystring param flag that if set calls the method below that I created which is basically a similar method as the above but with a bit of different logic in it:
protected void PlaceGoogleCheckoutOrder()
{
if (!IsValid)
return;
... rest of logic here, but I can't get to it because there is no event model to allow IsValid to work
}
Obviously I'm not tying in an event model to this therefore once it hits the check for Page.IsValid it errors with the following message at runtime:
Page.IsValid cannot be called before validation has taken place. It should be queried in the event handler for a control that has CausesValidation=True and initiated the postback, or after a call to Page.Validate.
But I still want to be able to call this validation, the validation that's already been setup in our .aspx. I don't want to reinvent the wheel on this and I don't in this case want to use an ASP.NET based button (do not ask me why, I have my reasons and it's too long to get into that).
I want to know how I can still get that Page.IsValid check to work for a non-event driven button using . I'm not sure how to hook up an event to do so that still hooks in after the redirect and allows that code to still validate.
I tried adding Page.Validate(); inside my PlaceGoogleCheckoutOrder() method right before the check for Page.IsValid but I still get the same error.
After looking at MSDN on Page.Validate() (http://msdn.microsoft.com/en-us/library/0ke7bxeh.aspx) and it states "The validation group is determined by the control that posted the page to the server. If no validation group is specified, then no validation group is used."
So that's why nothing happened. So I'm not sure how to get ASP.NET in this case to know about the control (in this case my ) that posted the page to the server so that a validation group IS used. I guess I could add a runat="server" to my ...but doubt that's all I need to do here.
The trick with your normal button is that it never does a post back because your href attribute has some other url there. If you want to check if the page is valid, you have to post back to your page class first to make that check and then redirect from there.
What you can do to make this happen with a normal anchor (<a >) tag is process that anchor's onclick event in javascript, do any client side work you want, and then call the __doPostBack() javascript function.
You can see an example of how to call __doPostBack() on msdn here:
http://msdn.microsoft.com/en-us/library/aa720099(VS.71).aspx
It's from .Net 1.1, but still accurate.
I have a ASP.NET Wizard running my checkout process of my shopping cart. I just added a Paypal Express checkout link to my 2nd step. The Paypal process takes the user away from the page and then redirects them back to my wizard when they're done. I'm parsing an HTTP parameter with Request.QueryString when the user comes back from Paypal to set the wizard to step 3. This loads just fine, but when I click on the Back button (of the wizard), it does a postback but stays on step 3. Can anyone think of a reason for this? The link it's referencing still has the HTTP parameters, but I'm checking for a postback prior to programmatically setting the wizard step based on the parameter. Does anyone have any experience with this?
Well, I'm not sure why it was doing it, but overriding the blackbox PreviousButtonClick event on the wizard with the following code fixed it. It seems to me like this should be the behavior the button was implementing anyway, but it wasn't. Weird.
Protected Sub wizSubmitOrder_PreviousButtonClick(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.WizardNavigationEventArgs) Handles wizSubmitOrder.PreviousButtonClick
Dim previousStepIndex As Integer = wizSubmitOrder.ActiveStepIndex - 1
wizSubmitOrder.MoveTo(wizSubmitOrder.WizardSteps(previousStepIndex))
End Sub
I have an asp.net server control (with the asp: in its definition). The button has been set to do post back.
On the server side, I have the on click event handler
e.g btnSave_click()
On the client side, I have a javascript function to be invoked on the click event
e.g btnSave.Attributes.Add("onclick","javascript: return CheckIsDirty();")
Am not sure which order these two will be executed. Because I want first on the client side to warn of any data entry fields that are not yet filled-out before actually saving any data.
Any help?
First client side, second server-side.
So you can use it.
I also use it in some cases, like:
close.Attributes["OnClick"] = "return confirm('Are you sure?')";
In this case if the user presses 'No' then the server-side event handler does not even play a role.
The trick here is to set this global variable "Page_IsValid" false if your test fails and this will stop the post back.
Read this page http://msdn.microsoft.com/en-us/library/aa479045.aspx which explains both server side and client Validation. There is sone good code example you can use.
The way you are setting your onClick JavaScript event will actually prevent it from posting back as you are overwritten the ASP.NET event handler. The correct way to accomplish the validation you are intending is to:
btnSave.Attributes.Add("onclick", "CheckIsDirty();" + GetPostBackEventReference(btnSave).ToString());
Notice that you append the result of GetPostBackEventReference, so that in JavaScript you first call your CheckIsDirty() method and then call the ASP.NET postback method. Assuming your method returns true, then the button will post. If it returns false then it will not cause a post back.
Does that sound like what you are trying to accomplish?
I think you need a much better understanding of what it means client side and what it means server side and how they all relate together. I've seen more and more developers make a mess of it.
Of course the client side will execute first in your case. Actually there's no way to execute it after the server code is executed (except if you do something manually). I'll try to give a brief explanation:
Whatever you have in your server, will generate some HTML on the client and the user is always interacting on the client. So you have a html button that the user is clicking. What the browser will do is execute the javascript associated with it or if no javascript is specified and the button is a submit button it will submit the form. if you check the generated html you will see that for the onclick event you will have the script you have added followed by some autogenerated script that actually will submit the form to the server. Your server side code will execute only if the page will be submitted.