Asp.net MVC 3 - dropdownlist from database with selectedvalue

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I am new to MVC and am wondering if someone can please help?

I have the following which populates the DropDownList for each row in the model yet does not set the selected value (tblcusts.typeid) in the DropDownList when the page is populated. Any assistance would be greatly appreciated.

What I have tried:

Models

public class tblcusts
{
   [Key]
   public int custid { get; set; }
   public int typeid { get; set; }
}

public class tblcusttypes
{
  [Key]
  public int typeid { get; set; }
  public string name { get; set; }
  public bool active { get; set; }
}

View

@Model IList<MvcApplication1.Models.tblcusts>
@for (var i = 0; i < Model.Count; ++i)
    {
       @Html.DropDownList("typeid", (IEnumerable<SelectListItem>)ViewBag.customertype)
       <br />
    }

Controller

var result = from m1 in db.custs select m1;

var query = from m2 in db.custtypes where m2.active == true orderby m2.name select m2.name;
var CustomerTypeList = new List<string>();
CustomerTypeList.AddRange(query.Distinct());
ViewBag.customertype = new SelectList(CustomerTypeList);

return View(result.ToList());

Posted 26-May-17 8:42am

Timothy Vandeweerd

Updated 26-May-17 9:10am

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David_Wimbley · Answer 1 · 2017-05-26T09:10:00

Solution 1

Your not getting the selected value because your not setting any selected value. Also, your view is confusing, your looping over the drop down list in your view, you should be doing that in your model or controller (preferably model)....but not i guess its to show 1 type drop down per customer? Anywho...

To set the selected value on SelectList's you need to do something like this.

C#

List<string> dropdown_content = new List<string>();
var query = from m2 in db.custtypes where m2.active == true orderby m2.name select m2.name;
SelectList list = new SelectList(query);

// This is where you find the selected item and if it isn't null, set Selected == true
var selectedItem = list.FirstOrDefault(m=>m.Value == id);

if(selectedItem != null)
{
   selectedItem.Selected = true;
}    

ViewBag.customertype = list;

Posted 26-May-17 9:10am

David_Wimbley

Comments

Timothy Vandeweerd 26-May-17 16:00pm

Thank you David, I changed:

from: var selectedItem = list.FirstOrDefault(m => m.Value == id);
to: var selectedItem = list.FirstOrDefault(m1 => m1.Value == typeid);

The error highlights the assignment "== typeid);" and shows: "The name 'typeid' does not exist in the current context"

Am I understanding things properly? My view will list rows from tblcusts (m1) and each row will have a DropDownList showing all the rows from tblcusttypes (m2) with the SelectedValue set based on the rows value of tblcusts.typeid which will can be different for each row of tblcusts.

David_Wimbley 27-May-17 2:46am

Is typeid a variable? In your code sample its a string. Without knowing more about your code, it looks like you need to loop over tblcusts which is what your view has as its Model, that for loop in your view. Loop through that in your Model class, decide if the value is there and set Selected == true.

SelectList has the following properties on it. Text, Value, Selected. Value being what is saved, Text what is displayed and Selected to indicate if anything has been selected.

You'll need to do a comparison to say "Does my value in the select list match my value from the database, if so -> .Selected is set to true".

Timothy Vandeweerd 29-May-17 9:49am

David,

Thank you for your response. typeid is an int column in both tables. It is a Primary Key in tblcusttypes and a Foreign Key in tblcusts. My view will display multiple rows when the page is loaded and for each row in tblcusts I would like to have a DropDownList and the SeclectedValue to be set to the Foreign Key value. Thank you for your time, I have been searching and searching and cannot seem to find an example of this online.

This is my code:

Models

public class tblcusts
{
[Key]
public int custid { get; set; }
public int typeid { get; set; }
}

public class tblcusttypes
{
[Key]
public int typeid { get; set; }
public string name { get; set; }
public bool active { get; set; }
}

View

@model IList<mvcapplication1.models.tblcusts>
@for (var i = 0; i < Model.Count; ++i)
{
@Html.DropDownList("typeid", (IEnumerable<selectlistitem>)ViewBag.customertype)
}

Controller

var result = from m1 in db.custs select m1;

var query = from m2 in db.custtypes where m2.active == true orderby m2.name select m2.name;
var CustomerType4= new List<string>();
CustomerType4.AddRange(query.Distinct());
ViewBag.customertype = new SelectList(CustomerType4);

David_Wimbley 29-May-17 15:16pm

Hey Timothy,

Looks like in your controller you need to loop over ViewBag.customertype to set what is selected. I'd make the following changes.

Instead of


ViewBag.customertype = new SelectList(CustomerType4);

I would change it to


var selectList = new SelectList(CustomerTyp4);
foreach(var item in selectList)
{
   if(item.Value == typeid)
   {
     item.Selected = true;
   }
}

Timothy Vandeweerd 29-May-17 15:32pm

David, thank you but now the line below produces an error:

if (item.Value == typeid)

Error: The name 'typeid' does not exist in the current context

I really appreciate your time on this.

David_Wimbley 29-May-17 16:52pm

No problem, happy to help.

Yea thats the problem is typeId is your variable. Thats what you are trying to say is your selected value. I don't have access to your whole code base and typeId is what you stated is "typeid is an int column in both tables. " so you've got to have the value that needs to be marked as selected somewhere.

In your controller/action you'd have something like


public ActionResult(int id)
{
    var typeId = id;
}

Where the id passed into your action is the record you are trying to display on your screen.

For testing purposes, i suggest you hard code typeid to whatever value exists in your database so you can see how the selecting item in SelectList works. From there, figure out how you know what record is marked to select. This part i can't help you with as I don't have access to your code nor do i know what your project is.

Hopefully that steers you in the right direction

Timothy Vandeweerd 30-May-17 9:49am

David, thanks again. Below is my entire code. There is no id passed to the action. When the page is loaded it shows a list of customers and for each row I would like to have the SelectedValue for each rows DropDownList to be set. The source for the rows is the table tblcusts. The source for each rows DropDownList is the table tblcusttypes. Is this not possible?

Models
------

public class tblcusts
{
[Key]
public int custid { get; set; }
public int typeid { get; set; }
}

public class tblcusttypes
{
[Key]
public int typeid { get; set; }
public string name { get; set; }
public bool active { get; set; }
}

View
----

@Model IList<mvcapplication1.models.tblcusts>
@for (var i = 0; i < Model.Count; ++i)
{
@Html.DropDownList("typeid", (IEnumerable<selectlistitem>)ViewBag.customertype)

}

Controller
----------
var result = from m1 in db.custs select m1;

var query = from m2 in db.custtypes where m2.active == true orderby m2.name select m2.name;
var CustomerTypeList = new List<string>();
CustomerTypeList.AddRange(query.Distinct());
ViewBag.customertype = new SelectList(CustomerTypeList);

return View(result.ToList());