Concat Value not is coming in mvc

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MVC3

when i send a textbox value like e.g. "23" and click submit button then View page does not return "23+" I want to print concatinate value of Textbox Value and Button value on view page. help me pls.

My View Code Is as follows:

@using (Html.BeginForm("GetName", "Default1"))
{
@Html.TextBox("name",(string)ViewBag.test)
<input type="submit" value="+" name="Btn_plus"/>
}

My Controller Code is as Follows:

public ActionResult GetName(string name, string Btn_plus)
       {
           ViewBag.test = name + Btn_plus;
           return View("Index");
       }