Few days ago I had a case when I needed to make FORM POST from my ASP.NET WebForms page to an external site URL. More specifically, I was working on implementing Simple Payment System (like Amazon, PayPal, MoneyBookers).
The operator asks to make FORM POST request to a given URL in their website, sending parameters together with
the post which are computed on my application level (access keys, secret keys, signature, return-URL… etc). So, since we are not allowed nesting another form inside
the <form runat=”server”> … </form>, which is required because other controls in my ASPX code work on server-side, I thought to inject
the HTML and create FORM with method=”POST”. After making some proof of concept and testing some scenarios, I’ve concluded that I can do this very fast in two ways: Using jQuery to create form on fly with
the needed parameters and make submit() Using HttpContext.Current.Response.Write to write
the form on server-side (code-behind) and embed JavaScript code that will do
the post Both ways seemed fine. 1. Using jQuery to create FORM html code and Submit it. Let’s say we have ‘PAY NOW’ button in our ASPX code: <asp:Button ID="btnPayNow" runat="server" Text="Pay Now" /> Now, if we want to make this button submit a FORM using POST method to another website,
the jQuery way should be as follows: <script src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.5.1.js" type="text/javascript"></script> <script type="text/javascript"> $(function () { $("#btnPayNow").click(function (event) { event.preventDefault(); //construct htmlForm string var htmlForm = "<form id='myform' method='POST' action='http://www.microsoft.com'>" + "<input type='hidden' id='name' value='hajan' />" + "</form>"; //Submit
the form $(htmlForm).appendTo("body").submit(); }); }); </script> Yes, as you see,
the code fires on btnPayNow click. It removes
the default button behavior, then creates htmlForm string. After that using jQuery we append
the form to
the body and submit it. Inside
the form, you can see I have set
the htttp://www.microsoft.com URL, so after clicking
the button you should be automatically redirected to
the Microsoft website (just for test, of course for Payment I’m using Operator's URL). 2. Using HttpContext.Current.Response.Write to write
the form on server-side (code-behind) and embed JavaScript code that will do
the post
The C# code
behind should be something like this: public void btnPayNow_Click(object sender, EventArgs e) { string Url = "http://www.microsoft.com"; string formId = "myForm1"; StringBuilder htmlForm = new StringBuilder(); htmlForm.AppendLine("<html>"); htmlForm.AppendLine(String.Format("<body onload='document.forms[\"{0}\"].submit()'>",formId)); htmlForm.AppendLine(String.Format("<form id='{0}' method='POST' action='{1}'>", formId, Url)); htmlForm.AppendLine("<input type='hidden' id='name' value='hajan' />"); htmlForm.AppendLine("</form>"); htmlForm.AppendLine("</body>"); htmlForm.AppendLine("</html>"); HttpContext.Current.Response.Clear(); HttpContext.Current.Response.Write(htmlForm.ToString()); HttpContext.Current.Response.End(); } So, with this code we create htmlForm string using StringBuilder class and then just write
the html to
the page using HttpContext.Current.Response.Write.
The interesting part here is that we submit
the form using JavaScript code: document.forms["myForm1"].submit() This code runs on body load event, which means once
the body is loaded
the form is automatically submitted. Note: In order to test both solutions, create two applications on your web server and post
the form from first to
the second website, then get
the values in
the second website using Request.Form[“input-field-id”] I hope this was useful post for you. Regards, Hajan
