Also:
- added a "Please wait..." label
- replaced "\\" (double back slash) with "/" (single forward slash) inside the foreach (the input tag closing)
- appended 5 blanks after "</html>" - for some reasons the Response.Write truncated the last 3 chars of the stringbuilder content, thus displaying a weird "/>" in the top of the page, although for a brief moment)
The final code is this:
public void Post(bool hidden)
{
// Build the HTML form
var form = new StringBuilder();
form.AppendFormat("<html><head></head><body onload=\"document.{0}.submit()\">", FormName);
form.AppendFormat("<form name=\"{0}\" method=\"POST\" action=\"{1}\" >", FormName, Url);
form.Append("<p><b>Please wait...</b></p>");
foreach (string key in Fields)
{
if (hidden)
form.AppendFormat("<input type=\"hidden\" name=\"{0}\" value=\"{1}\" />", key, Fields[key]);
else
form.AppendFormat("<input name=\"{0}\" value=\"{1}\" />", key, Fields[key]);
}
form.Append("</form></body></html> ");
// Clear all and return the form
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.Write(form.ToString());
HttpContext.Current.Response.Flush();
HttpContext.Current.Response.End();
}