On directly executing storedProcedure I am getting output as I need, but when I am accessing the stored Procedure from controller then It's giving me an error as 

An SqlParameter with ParameterName '@role' is not contained by this SqlParameterCollection.

below is my sp: 

ALTER procedure [dbo].[usp_login]
 @flag char(1)=null,
 @unm varchar(30)=null,
 @pwd varchar(128)=null,
 @salt varchar(30)=null,
 @syshashpwd varchar(128)=null,
 @role char(1)=null OUTPUT,
 @status int=null OUTPUT,
 @uid int=null OUTPUT
as
BEGIN
     .......
END

controller code: 

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Login(LoginVM entity)
{
    string OldHASHValue = String.Empty;
    string SALT = String.Empty;
    string expectedHashString = String.Empty;
    int status = 0;
    string role = string.Empty;
    int userid = 0;
    try
    {
        //using (db = new DBLoginEntities())
        //{  
        // Ensure we have a valid viewModel to work with  
        if (!ModelState.IsValid)
        {
            return View(entity);
        }

        var userInfo = String.Empty;//db.UserMasters.Where(s => s.Username == entity.Username.Trim()).FirstOrDefault();  
        var saltVAL = String.Empty;//db.tblsalts.FirstOrDefault();

        //Retrive SALT Value From Database
        using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["roconstr"].ConnectionString))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = "usp_login";
                cmd.Connection = conn;
                cmd.Parameters.AddWithValue("@flag", "S");
                conn.Open();
                using (SqlDataReader dr = cmd.ExecuteReader())
                {
                    while (dr.Read())
                    {
                        SALT = dr["saltvalue"].ToString();
                    }
                }
                conn.Close();
            }
        }

        //Generate Hashed Pwd
        expectedHashString = Get_HASH_SHA512(entity.Password, entity.Username, SALT);

        //Pass values to usp_login procedure to validate user
        using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["roconstr"].ConnectionString))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = "usp_login";
                cmd.Connection = conn;
                cmd.Parameters.AddWithValue("@flag", "L");
                cmd.Parameters.AddWithValue("@unm", entity.Username);
                cmd.Parameters.AddWithValue("@pwd", entity.Password);
                cmd.Parameters.AddWithValue("@salt", SALT);
                cmd.Parameters.AddWithValue("@syshashpwd", expectedHashString);
                cmd.Parameters["@role"].Direction = ParameterDirection.Output;
                cmd.Parameters["@status"].Direction = ParameterDirection.Output;
                conn.Open();
                cmd.ExecuteNonQuery();
                conn.Close();

                status = Convert.ToInt32(cmd.Parameters["@status"].Value);
                if (status == 0)
                {
                    //Login Fail
                    ViewBag.Message = string.Format("Access Denied! Wrong Credential");
                    //TempData["ErrorMSG"] = "<script>alert('Access Denied! Wrong Credential');</script>";  
                    return View(entity);
                }
                else
                {
                    role = Convert.ToString(cmd.Parameters["@role"].Value);
                    userid = Convert.ToInt32(cmd.Parameters["@uid"].Value);
                    SignInRemember(entity.Username, entity.isRemember);

                    //Set A Unique ID in session
                    Session["UserID"] = userid;
                    Session["UserRoll"] = role;
                    Session["Username"] = entity.Username;

                    // If we got this far, something failed, redisplay form  
                    return RedirectToAction("Dashboard", "Dashboard");
                }

            }
        }
        // }  
    }
    catch
    {
        throw;
    }
}