using linq query to select count

how to write the below code using Linq query 




string str = "select Vendor_Id,UserName,count(*) from tblvendor where UserName='" + txt_UserName.Text + "'and BINARY Password='" + txt_Password.Text + "'";
 MySqlCommand cmd = new MySqlCommand(str, con);
 MySqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows)

                {

                    while (dr.Read())

                    {

                        VendorId = Convert.ToInt32(dr["Vendor_Id"]);

                        Session["vendorusername"] = dr["UserName"].ToString();

                        UserName = dr["UserName"].ToString();

                        Session["vusername"] = UserName;

                    }

                }