Use htmlhelper to get action in BeginForm() Method of ASP.NET MVC 3

You can use ILSpy or any other reflector and see what is happening in Html.BeginForm

I just copy paste the code for you.

// System.Web.Mvc.Html.FormExtensions
/// <summary>Writes an opening &lt;form&gt; tag to the response. When the user submits the form, the request will be processed by an action method.</summary>
/// <returns>An opening &lt;form&gt; tag. </returns>
/// <param name="htmlHelper">The HTML helper instance that this method extends.</param>
public static MvcForm BeginForm(this HtmlHelper htmlHelper)
{
    string rawUrl = htmlHelper.ViewContext.HttpContext.Request.RawUrl;
    return htmlHelper.FormHelper(rawUrl, FormMethod.Post, new RouteValueDictionary());
}


// System.Web.Mvc.Html.FormExtensions
private static MvcForm FormHelper(this HtmlHelper htmlHelper, string formAction, FormMethod method, IDictionary<string, object> htmlAttributes)
{
    TagBuilder tagBuilder = new TagBuilder("form");
    tagBuilder.MergeAttributes<string, object>(htmlAttributes);
    tagBuilder.MergeAttribute("action", formAction);
    tagBuilder.MergeAttribute("method", HtmlHelper.GetFormMethodString(method), true);
    bool flag = htmlHelper.ViewContext.ClientValidationEnabled && !htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled;
    if (flag)
    {
        tagBuilder.GenerateId(htmlHelper.ViewContext.FormIdGenerator());
    }
    htmlHelper.ViewContext.Writer.Write(tagBuilder.ToString(TagRenderMode.StartTag));
    MvcForm result = new MvcForm(htmlHelper.ViewContext);
    if (flag)
    {
        htmlHelper.ViewContext.FormContext.FormId = tagBuilder.Attributes["id"];
    }
    return result;
}

If you want an action attribute from @Html.BeginForm() without any parameters you can use jquery. I use this to ajax post a form inside jqueryUI dialogs.

var form = $('form'); //get the form
var actionUrl = $('form').attr('action'); //get the action url

And then you can use POST

 $.ajax({
      type: "POST",
      url: actionUrl,
      data: form.serialize(),                                    
      success: function (data, status, xhr) {
                if (data.Sucess) {
                   //do something
               } else {
               }
      }
})  

Regards.

use htmlhelper argument

public class myBeginForm : IDisposable
{
    private HtmlHelper _myHtmlhelper;
    public myBeginForm (HtmlHelper htmlHelper, [you can add your need argument here] )
    {
        _myHtmlhelper= htmlHelper;
        var container = new TagBuilder("form");

       /// your Code 
    }

    public void Dispose()
    {
        myHtmlhelper.ViewContext.Writer.Write("</form>");
    }
}