MVC4 Razor( How To get a specific value from database

Question

i am using entity data model in mvc 4,i want specific value from dabase like as(select username from Emp where RollId="Textbox1.text")

but in mvc code

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1.[view file code]-->GetResultView

@using(Html.BeginForm("GetResult","Login",FormMethod.Post))

{

<div>

@Html.TextBoxFor(Model=>Model.UserName)

</div>

<div>

@Html.DisplayFor(Model=>Model.RollId)

</div>

<div>

<input type="submit" value="GetResult" name="GetResult">

</div>

}

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 2.[Controller]

public ActionResult GetResult()

{

return View();

}

[HttpPost]

public ActionResult GetResult(EmpInfo_Tbl ET)

{

using (db)

{

var v = db.EmpInfo_Tbl.Where(u => u.UserName.Equals(ET.UserName)).Select(u =>u.RollId).FirstOrDefault();

ViewBag.RollId = v.ToString();

}

return View(ET);

}

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 But in all thing i get value zero...but i didnt get excatly  values..so plz help me to find out..:)