public static MvcHtmlString SendMailTo(this HtmlHelper helper, string emailAddress, string subject, string displayText)
    {
        var sb = string.Format("<a href="{0}{1}{2}" title="{1}">{3}</a>",
            CharEncode("mailto:"), CharEncode(emailAddress),CharEncode("?subject=" +subject), CharEncode(displayText));

        return new MvcHtmlString(sb);
    }

    public static string CharEncode(string value)
    {
        var enc = System.Text.Encoding.Default;
        var retval = "";
        for (var i = 0; i < value.Length; i++)
        {
            retval += "&#" + enc.GetBytes(new[] { Convert.ToChar(value.Substring(i, 1)) })[0] + ";";
        }
        return retval;
    }

<div class="form-group">
                    @Html.LabelFor(m => m.ApplicationId, new { @class = "col-sm-3 control-label" })
                    <div class="col-sm-8">
                        @Html.TextBoxFor(m => m.ApplicationId,  new {@class = "form-control"})
                    </div>
                </div>
              <div class="form-group">
                <div class="col-sm-11" style="text-align:right">
                    @Html.SendMailTo("info@test.com", "Password Request: ", "Request Password")
                    <button type="submit" class="button">Sign in</button>
                </div>
              </div>

`$('.class of your textbox').val()' //will return a string

c.1 Place your partial view in a `div element`
   c.2 Make an `ajax` call from `jquery` to an action which returns your partial view filled with data

      Example for c.2:

           *AJAX*

           $.ajax({
              type:"GET",
              data:{
                  mail:$('.class of your textbox').val()
              },
              success: function(response){
                 $(".class of your div").html(response.Html);
              }
              error: function(response){
                 // whatever you want to do
              }
           });

          *Controller Action*

           public JsonResult(string mail)
           {

              var model = new CustomModel(){ Mail=mail };  // custom class to your as model for your partial view

              var html = RenderPartial(...)  // method you can find in the link posted below
              return Json(
              {
                Html=html
              },JsonRequestBehavior.AllowGet)
           }