Win Win - 10 days ago 7
C# Question

Populating a razor dropdownlist from a List<object> in MVC

I have a model:

public class DbUserRole
{
public int UserRoleId { get; set; }
public string UserRole { get; set; }
}

public class DbUserRoles
{
public List<DbUserRole> GetRoles()
{
BugnetReports RoleDropDown = new BugnetReports();
List<DbUserRole> Roles = new List<DbUserRole>();
DataSet table = RoleDropDown.userRoleDropDown();
foreach (DataRow item in table.Tables[0].Rows)
{
DbUserRole ur = new DbUserRole();
ur.UserRole = Convert.ToString(item["UserRoleName"]);
ur.UserRoleId = Convert.ToInt32(item["UserRoleID"]);
Roles.Add(ur);
}
return Roles;
}
}


And here is the Controller that loads the view:

//
// GET: /Admin/AddNewUser

public ActionResult AddNewUser()
{
DbUserRoles Roles = new DbUserRoles();
return View(Roles.GetRoles());
}


I can get the items in the list to display using a
@foreach
loop as shown below:

@foreach (var item in Model)
{
<tr>
<td>
@item.UserRoleId
</td>
<td>
@item.UserRole
</td>
</tr>
}


But how do I populate a dropdownlist with the model that is passed through, I have tried

@Html.DropDownListFor(x => x.UserRole)


but I'm having no luck.

Answer

You can separate out your business logic into a viewmodel, so your view has cleaner separation.

First create a viewmodel to store the Id the user will select along with a list of items that will appear in the DropDown.

ViewModel:

public class UserRoleViewModel
{
    // Display Attribute will appear in the Html.LabelFor
    [Display(Name = "User Role")]
    public int SelectedUserRoleId { get; set; }
    public IEnumerable<SelectListItem> UserRoles { get; set; }
}

References:

Inside the controller create a method to get your UserRole list and transform it into the form that will be presented in the view.

Controller:

private IEnumerable<SelectListItem> GetRoles()
{
    var dbUserRoles = new DbUserRoles();
    var roles = dbUserRoles
                .GetRoles()
                .Select(x =>
                        new SelectListItem
                            {
                                Value = x.UserRoleId.ToString(),
                                Text = x.UserRole
                            });

    return new SelectList(roles, "Value", "Text");
}

public ActionResult AddNewUser()
{
    var model = new UserRoleViewModel
                    {
                        UserRoles = GetRoles()
                    };
    return View(model);
}

References:

Now that the viewmodel is created the presentation logic is simplified

View:

@model UserRoleViewModel

@Html.LabelFor(m => m.SelectedUserRoleId)
@Html.DropDownListFor(m => m.SelectedUserRoleId, Model.UserRoles)

References:

This will produce:

<label for="SelectedUserRoleId">User Role</label>
<select id="SelectedUserRoleId" name="SelectedUserRoleId">
    <option value="1">First Role</option>
    <option value="2">Second Role</option>
    <option value="3">Etc...</option>
</select>