Although I don't consider myself a web programmer, I've done a fair amount of web programming, so I'm almost embarrassed to ask what is wrong with the below code. There is something fundamental about ASP.NET that I must be missing.
I have two pages, source.aspx and destination.aspx:
source.aspx - html:
<body>
<form id="form1" action="destination.aspx" method="post" runat="server">
<input id="Text1" type="text" />
<input id="Text2" type="text" />
<input id="Checkbox1" type="checkbox" />
<input id="Submit1" type="submit" value="submit" />
</form>
</body>
destination.aspx - code behind:
protected void Page_Load(object sender, EventArgs e)
{
// Below variable gets assigned null.
string text1 = Request.Form["Text1"];
}
When I submit the source.aspx form, once it gets to the destination.aspx form, there is no information in the FORM variables. I thought that the forms 'runat="server" ' would ensure that I ended up in the ASP.NET page pipeline, and in fact I can step through this code. There are no POSTed form variables other than viewstate, and the PARAMs collection doesn't have anything corresponding to control data either, not even ones that would correspond to decorated control names. The question is, what is happening that is making my POSTed variables 'disappear', at least to the destination page?
I'm not looking for alternatives how to make this work (i.e. make the controls server controls with runat="server", etc). I can fix the problem. What I am trying to determine is 'what is it about ASP.NET that makes my controls not appear to be receivable by the destination page. Thanks - I thought that I understood HTTP pretty well, but there seems to be a little sleight of hand courtesy of ASP.NET that I'm not seeing.
You can remove the runat="server" off of your form tag since you want to opt out of what ASP.NET gives you with server controls. You are basically thinking correctly that this should work without needing all the ASP.NET page processing bits.
It's a small change you need to make - you need to use 'name' instead of 'id' on your input controls in order for them to appear in the Form collection. It's a subtle thing but I believe it's not exclusive to ASP.NET - the name attribute specifies what to associate the value with in the POST variable collection.
Consult HTML input - name vs. id for more information on id vs. name
Good luck
Request.Form uses name attribute from elements. So you should write name attributes to each of the html elements.
<body>
<form id="form1" action="destination.aspx" method="post" runat="server">
<input id="Text1" name="Text1" type="text" />
<input id="Text2" name="Text2" type="text" />
<input id="Checkbox1" name="Checkbox1" type="checkbox" />
<input id="Submit1" type="submit" value="submit" />
</form>
</body>
Related
Having lived in an MVC world for the last few years I just cannot get my head back into a WebForms world.
I have to try to integrate an external payment getway into a 4 step process. The last step involves POSTing some values to a given URL. This URL is expecting a preset list of values with predefined names (i.e. I cannot change what it is expecting).
The problem I am having is populating values gained from steps 1-3 on the form I want to post.
Let's say I need to send 3 values (there are more but the principle is the same):
- amount
- returnurl
- name
I could write a form along the lines of
<form action="http://url/goes/here">
<p>Please confirm the details below</p>
<asp:TextBox id="amount" runat="server" />
<asp:TextBox id="returnurl" runat="server" />
<asp:TextBox id="name" runat="server" />
<asp:Button id="submitme" />
</form>
And easily pre-populate the textboxes (or labels, or whatever I need) from the codebehind on PageLoad.
But then the values are submitted with prefixed with the 'ctl00$ContentBottom$WebFormControl$ctl00$' and so the external url throws it away and complains no values have been supplied. It sees 'ctl00$ContentBottom$WebFormControl$ctl00$amount' and not 'amount'.
Is there anyway I can amend the names of the values that are posted?
instead of amending the names of value you can add them in your aspx page as follows
<input type="hidden" name="billing_cust_name" value="<%=txtbox1.Text%>">
<input type="hidden" name="billing_cust_address" value="<%=txtbox2.Text%>" >
<input type="hidden" name="billing_cust_email" value="<%=txtbox3.Text%>">
<input type="hidden" name="billing_cust_notes" value="<%=txtbox4.Text%>">
When the form is ready to be posted change the value and then post.
I have a simple ASP.NET page with a MasterPage. Within the MasterPage, I have two login fields:
<input type="text" runat="server" id="txtUserName"/>
<input type="text" runat="server" id="txtPassword"/>
When the controls are rendered to the page, ASP.NET renders the following:
<input type="text" runat="server" id="ctl00_txtUserName" name="ctl00$txtUserName"/>
<input type="text" runat="server" id="ctl00_txtPassword" name="ctl00$txtPassword"/>
If I understand correctly, the name attribute corresponds to the UniqueID property of a control. However, when I'm debugging Page_Load and attempt to view the UniqueID of these fields, they have different values (ctl0$txtUserName and ctl0$txtPassword respectively)!
Note that this does not seem to be an issue on all pages using this MasterPage. Most of them work correctly and use ctl0$txtUserName and ctl0$txtPassword in both rendering and Page_Load.
Any idea what might cause ASP.NET to render a different UniqueID for a control than it uses in Page_Load?
I'm still not sure what was causing the generated UniqueIDs in the MasterPage to be different in Page_Load than when rendered to the page. However, I was able to get around the issue by storing the UniqueIDs of these fields in hidden fields. I was then able to access the values directly in the Request.Form collection.
In other words, I did this:
In the MasterPage -
<input type="text" runat="server" id="txtUserName"/>
<input type="text" runat="server" id="txtPassword"/>
<input type="hidden" id="txtUserNameUID" value="<%=txtUserName.UniqueID%>"/>
<input type="hidden" id="txtPasswordUID" value="<%=txtPassword.UniqueID%>"/>
During Page_Load of the child page -
string username = Request.Form[Request.Form["txtUserNameUID"]];
string password = Request.Form[Request.Form["txtPasswordUID"]];
Hope this helps anyone else struggling with UniqueID weirdness in ASP.NET!
Weird quirk I just became aware of: any wrapping controls that are runat server must also have IDs. For instance, if you have a panel around the control, i.e. whatever "ctl00" is, it must be assigned an ID. If it is not set, it will be allocated one and this can change.
I found this article on MSDN talking about Cross-page posting.
I never worked with Page.PreviousPage. But I think its interesting.
Do you use it? Is it a good pratice, or a bad idea?
What do you think about?
Thanks.
The cross page posting is a helper to post some data to a different page and still have the asp.net code behind functionality.
Why is this exist ? because asp.net have a limitation of one and only form per page. But actually to an html page you can have many forms and many different post to different pages.
So to give a tool to that case, is let you set a second page to post the data, and you setup this on the Button (and not by placing second form), and from there is solve this issue, to post the data to a different page.
For example... with out asp.net and with simple html on a page you can do that.
<body>
<form method="post" action="samepage.html">
Username: <input type="text" name="user" />
<input type="submit" value="Submit" />
</form>
<form method="post" action="page_b.html">
email for news letter: <input type="text" name="email" />
<input type="submit" value="Submit" />
</form>
</body>
To solve a situation like this, and because asp.net not allow two forms at the same page, gives this option.
<body>
<form id="form1" runat="server">
Username: <asp:TextBox runat="server" ID="Name" />
<asp:Button runat="server"/>
email for news letter: <asp:TextBox runat="server" ID="email" />
<asp:Button runat="server" PostBackUrl="page_b.aspx" />
</form>
</body>
In the second case, you have one form, but you set the PostBackUrl to a different page, and from there asp.net still handle the data on code behind direct on a second page (with out redirect).
I hope this example gives you and an idea where to really use the previous page. Also what is more usually is the Redirect, how ever there are case that you need to have the result to a different page. So its per case if you use it or not.
I have an application into which I wish to allow users to enter login details for their own websites. One of authentication methods is 'forms'. The way I had envisaged it working, is the users entering the method & action of their login form, and the name/value for each credential item, e.g. one for username, one for password. My application would then post this data in order to simulate a login, get the returned authentication cookie and be able to work on their site as if logged in.
In principle, this sounded like a reasonable kind of thing to do. However, as I'm sure you're aware, ASP.NET has a lot of inputs, and also hidden ones, e.g. __VIEWSTATE, which are all always posted back to the server whenever the ASP.NET form is submitted e.g. when a real user logs in. When my app tries to login however, it doesn't have the full list of inputs on that page, and their values, e.g. the always changing __VIEWSTATE.
My question: is there a way to post data to an ASPX page, posting only certain inputs, and excluding others, e.g. __VIEWSTATE?
If the page were, say, PHP it would probably look like this:
Ex. 1:
...
<div id="header">
<form action="search.php" action="POST">
<div id="search">
<input type="text" name="query" id="SearchQueryText" value="Search query" />
<input type="button" name=submit" id="SearchSubmitButton" value="Search!" />
</div>
</form>
<form action="login.php" action="POST">
<input type="text" name="uname" id="Username" value="Username" />
<input type="text" name="passwd" id="Password" value="Password" />
<input type="button" name=submit" id="LoginSubmitButton" value="Login" />
</form>
...
</div>
...
in ASP.NET Web Forms, however, through the use of server controls, it'd probably look like:
Ex. 2:
...
<body>
<form name="AspNetForm" method="post" action="/Products/SomethingOrOther.aspx" id="Form" enctype="multipart/form-data">
<div id="header">
<div id="search">
<input type="text id="ctl00$SearchComponent$SearchBox" name="ctl00$SearchComponent$SearchBox" value="Search query" />
<input type="submit" id="ctl00$SearchComponent$SearchSubmit" name="ctl00$SearchComponent$SearchSubmit" value="Search!">
</div>
<div id="login">
<input type="text id="ctl00$LoginComponent$Username" name="ctl00$LoginComponent$Username" value="Username" />
<input type="text" id="ctl00$LoginComponent$Password" name="ctl00$LoginComponent$Password" value="Password">
<input type="submit" id="ctl00$LoginComponent$LoginSubmit" name="ctl00$LoginComponent$LoginSubmit" value="Login">
</div>
</div>
...
</form>
</body>
...
With example 1, submitting the login form is a simple case of POSTing uname=something&passwd=somethingelse to login.php, however, in ASP.NET, because all inputs are wrapped in a 'global' <form>, to submit the login inputs, you have to submit the global form, and therefore all the inputs.
So what I'm after, is a way to submit only certain inputs in that global form, e.g. not __VIEWSTATE, which we can't know without probing the page beforehand.
You can use AJAX to post back the values to a specific page. In general, Web Forms is designed to post back all data on the page when you trigger a server side event. You then choose which elements/values to use in your code. If you don't want to use view state on a element, you can disable it (e.g. EnableViewState=False).
You can use asp.net page same as asp classic.
In html action you can put the aspx page from and then you have to take that.
then you can use request object of asp.net to retrive data from form. Same you can create a html form in string and put that via putting it into panel control.
Then you can asp.net button as submit button.
I have an html page that I am converting over to an asp .net page. This page contained a form that accesses an external website that I have no control over. There is some sample code below:
<asp:Content ID="sample" ContentPlaceHolderID="body" Runat="Server">
<form name="Subscribe" method="post" action="http://anexternalwebsitehere.com/subscribe.asp">
<input type="text" name="email" size="45" maxlength="120" />
<input type="submit" name="submit" value="Subscribe" />
</form>
</asp:Content>
The form is more complicated than the example I have provided, but it gives a rough idea of what i need to convert over. Here are the problems I have encountered.
If I leave it as is:
When you click on the submit button you have a postback to the current page and not to the external page
If simply convert everything over to be asp form controls and change the postback url:
The id's become some convoluted "ctl00_body_ctl00" which the external page is not able to interpret.
Note: I do need the page to be an aspx page because I am using a master page for other content on the page.
Additional note: this is not Microsoft MVC.
What am I missing?
The issue was with nested forms as others have mentioned.
I was able to fix all my issues by simply doing the following:
Remove the extra form element i was adding.
Leave all controls as simply html controls, except for the submit button.
Replace the submit button with an asp .net button, and set the postback url.
The old code is as follows:
<asp:Content ID="sample" ContentPlaceHolderID="body" Runat="Server">
<form name="Subscribe" method="post" action="http://anexternalwebsitehere.com/subscribe.asp">
<input type="text" name="email" size="45" maxlength="120" />
<input type="submit" name="submit" value="Subscribe" />
</form>
</asp:Content>
The new code:
<asp:Content ID="sample" ContentPlaceHolderID="body" Runat="Server">
<input type="text" name="email" size="45" maxlength="120" />
<input type="submit" name="submit" value="Subscribe" />
<asp:button postbackurl="http://anexternalwebsitehere.com/subscribe.asp" text="Subscribe" runat="server" />
</asp:Content>
This fixes any of the issues with invalid nested forms as there are none. It also addresses the issue of asp .net renaming the asp elements because the only control that is being renamed is the asp button control which was not necessary for the submission to succeed.
Since you probably have the server form tag on your masterpage spanning your contentplaceholder, this new form you're declaring will be placed inside the server-form (by server-form i mean the one asp.net use for postbacks with runat="server")
I've had cases when i needed a special non-server form on an aspx page that already had a server-form, and the way i solved the problem was to place this non-server form outside the server-form - what i mean is, place it after the server-form. Since you use masterpages, you will need a new contentplaceholder on that masterpage, you can call it "noform". It is placed after the server-form so any content put in this noform will be placed outside the server-form. This mean no asp.net controls will work in this specific contentplaceholder (noform) since they won't be picked up by the framework, but you will be able to place your non-server form there and do your magic on that.
The problem, as you've probably guessed, is that you've got one form inside another form - ie the legacy form is appearing inside the ASP.NET form required by the master page.
One quick (if rather clunky) way to get around this is to close the ASP.NET form above the legacy form, and then open a new form below the legacy form. This means you've got three forms on the page, none of which are nested.
So you end up with something like this:
<asp:Content ID="sample" ContentPlaceHolderID="body" Runat="Server">
</form>
<form name="Subscribe" method="post" action="http://anexternalwebsitehere.com/subscribe.asp">
<input type="text" name="email" size="45" maxlength="120" />
<input type="submit" name="submit" value="Subscribe" />
</form>
<form method="post" action="myAspNetPage.aspx">
</asp:Content>
The closing </form> tag at the start closes the ASP.NET from the master page. You then have your form, which should now work as expected. Then the open <form> tag at the end simply ensures that the closing </form> tag from the master page is valid HTML.
Obviously anything appearing on the master page after the legacy form won't be within the standard ASP.NET form, so this may not work for you depending on how the rest of your page is structured.
It's not a particularly elegant solution, but it works as a quick fix (depending on what else is on your master page). We've used it where we had one legacy form required on a site with hundreds of pages, so we simply wanted a one-off fix rather than anything that affected the master page itself.
In our case, we couldn't change the legacy form as this was supplied by a third-party, regularly changed, and needed to be dropped into the ASP.NET page without a developer getting involved to amend it (eg as opposed to Brian's solution to his own question which requires editing the form and is clearly a better option in his case - and probably in most other cases where there is a similar problem).
Your button's click event will handle submission of the url and data.
//C# source
protected void button_Click(object sender, EventArgs e)
}
string customURL = "http://anexternalwebsitehere.com/";
string emailValue = textBoxEmail.Text; //of course validate this for proper email...
customURL += "page.aspx?email=" + emailValue;
Response.Redirect(customURL);
}