I recieve my ID double while Editing the Dropdown

Question

I create my Branch,where i choose Dropdown to select my Company, in dropdown i bind Company ID and Company Name.When i create my Edit function.I filled all my required fields,When I click on my Edit button,I found my com_id double, eg:04 is my real ID and I get "0404", now how can i resolve it?

 

Here is my Controller

public ActionResult Edit(string id)
{
    Branch model = new Branch();
    var br = erkDB.m_br.FirstOrDefault(x => x.br_id == id);
    model.br_id = id;
    model.br_nam = br.br_nam;
    model.br_add = br.br_add;
    model.br_eml = br.br_eml;
    model.br_fax = br.br_fax;
    model.br_mob = br.br_mob;
    model.br_typ = br.br_typ;
    model.com_id = br.com_id;
    var com = erkDB.m_com.ToList();
    foreach (var item in com)
    {
        Company company = new Company();
        company.com_nam = item.com_nam;
        company.com_id = item.com_id;
        model.comModel.Add(company);
    }
    return View("Create", model);

}
[HttpPost]
public ActionResult Edit(Branch model)
{
    if (ModelState.IsValid)
    {

        var br = erkDB.m_br.FirstOrDefault(x => x.br_id == model.br_id);
        var temp = Request.Form["com_id"].ToString();
        string strNew = temp.Replace(",", "");
        //br.br_id = br;
        br.br_nam = model.br_nam;
        br.br_pho = model.br_pho;
        br.com_id = strNew;
        br.br_web = model.br_web;
        br.br_mob = model.br_mob;
        br.br_eml = model.br_eml;
        br.br_fax = model.br_fax;
        br.br_typ = model.br_typ;
        // mvcdb.m_com.Add(company);
        erkDB.SaveChanges();
        return RedirectToAction("Index");
    }
    return View("Create", model);

}