populating a drop down from a database

Question

So I am writing a basic mock website (my first one) and I am trying to populate a list from a database table.

In my controller I have;

public void patientInit()
    {
        hospitalSQLEntities db = new hospitalSQLEntities();
        ViewData["bloodtypeList"] = db.bloodtypes.ToList();
        ViewData["doctorno"] = "";
        ViewData["wardno"] = "";
        ViewData["patientid"] = "";
        ViewData["patientname"] = "";
        ViewData["address"] = "";
        ViewData["gender"] = "";
        ViewData["bloodtype"] = 0;
        ViewData["spam"] = "";
        ViewData["organs"] = "";
        ViewData["formmessage"] = "";
    }

And in my page I've written this

<label for="bloodtype">Blood Type:</label>
                <select name="bloodtype"  >
                            <% List<InAmberClad.Models.bloodtype> bloodtypeList = (List<InAmberClad.Models.bloodtype>) ViewData["bloodtypeList"];
                               foreach (InAmberClad.Models.bloodtype st in bloodtypeList)
                                { 
                            %>
                                <option value="<%= st.bloodcode%>" <%if (st.bloodcode==(String) ViewData["bloodtypeList"]) Response.Write("Selected"); %>>"><%Response.Write(st.meaning); %></option>
                            <%  } %>
                                <option value="0" <%if ((Int32) ViewData["bloodtype"]==0) Response.Write("Selected"); %>></option>
                </Select>

Any help with this would be greatly appreciated I've been stuck for hours and it's getting super frustrating!

Edit: The error code is surrounding the foreach loop, it says that the "NullReferenceException was unhandled by the user code. Object reference not set to an instance of an object."

Edit: Here is all of my controller code;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using InAmberClad.Models;

namespace InAmberClad.Controllers
{
[HandleError]
public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }

    public ActionResult patiententry()
    {
        return View();
    }
    public void patientInit()
    {
        hospitalSQLEntities db = new hospitalSQLEntities();
        ViewData["bloodtypeList"] = db.bloodtypes.ToList();
        ViewData["doctorno"] = "";
        ViewData["wardno"] = "";
        ViewData["patientid"] = "";
        ViewData["patientname"] = "";
        ViewData["address"] = "";
        ViewData["gender"] = "";
        ViewData["bloodtype"] = 0;
        ViewData["spam"] = "";
        ViewData["organs"] = "";
        ViewData["formmessage"] = "";
    }

    public void patientNewButtPressed()
    {
        if (Request.Params["submitter"] == "New Patient")
        {
            ViewData["doctorno"] = "";
            ViewData["wardno"] = "";
            ViewData["patientid"] = "(System Specified)";
            ViewData["patientname"] = "";
            ViewData["address"] = "";
            ViewData["gender"] = "";
            ViewData["bloodtype"] = 0;
            ViewData["spam"] = "";
            ViewData["organs"] = "";
            ViewData["formmessage"] = "";
        }
    }

    public void patientSearchByID()
    {
    }

    public void patientSearchByName()
    {
    }

    public void patientInsert()
    {
        hospitalSQLEntities db = new hospitalSQLEntities();
        int newid = 0;
        if (db.patients.Count() == 0)
            newid = 1;
        else
            newid = db.patients.Max(u => u.patientid) + 1;
        patient newpatient = new patient();
        newpatient.patientid = newid;
        newpatient.doctorno = Request.Params["doctorno"];
        newpatient.wardno = Request.Params["wardno"];
        newpatient.patientname = Request.Params["patientname"];
        newpatient.address = Request.Params["address"];
        newpatient.gender = Request.Params["gender"];
        newpatient.bloodtype = Request.Params["bloodtype"];
        newpatient.spam = Convert.ToInt32(Request.Params["spam"]);
        newpatient.organs = Convert.ToInt32(Request.Params["organs"]);
        db.AddTopatients(newpatient);
        db.SaveChanges();
    }

    public void patientUpdate()
    {
    }

    public ActionResult hospitalSQL()
    {
        patientInit();
        if (Request.Params["submitter"] == "New Patient")
            patientNewButtPressed();
        else if (Request.Params["submitter"] == "Search")
        {
            if (Request.Params["searchpatientid"].Length > 0)
                patientSearchByID();
            else if (Request.Params["searchpatientname"].Length > 0)
                patientSearchByName();
        }
        else if (Request.Params["submitter"] == "Cancel")
            patientInit();
        else if (Request.Params["submitter"] == "Save")
        {
            if (String.Compare(Request.Params["patientid"], "(System Specified)") == 0)
                patientInsert();
            else
                patientUpdate();
        }
        return View();
    }
}

}

Answer 1

If your view is strongly typed, you can use a helper:

@Html.DropDownListFor(m => m.bloodtype, Model.bloodtypelist)

Where bloodtype is the value and bloodtypelist is a List<T> that holds all the values populated from your db in your controller.

Edit:

Try the following:

<select name="bloodtype">
<% foreach (var st in (List<InAmberClad.Models.bloodtype>)ViewData["bloodtypeList"]) { %>
    <option value="<%=st.bloodcode%>" <%if (st.bloodcode==(String)ViewData["bloodtypeList"]){%> selected<%}%>><%=stmeaning%></option>
<% } %>
    <option value="0" <%if ((Int32)ViewData["bloodtype"]==0){%> selected<%}%>></option>
</select>

I'm guessing it's passing an empty list to the view.

Edit:

In your action, before View(); add patientInit();

Answer 2

Your life will become much easier if you would use strongly typed views, however you can create a drop list without them. Take a look at the signature for Html.DropDownList

Html.DropDownList(
    string name,
    IEnumerable<SelectListItem> selectList,
    string optionLabel,
    object htmlAttributes)