Setting selected value in SelectList isn't working using DropDownListFor

I am creating a SelectList for a drop down

public class EditDeviceViewModel
{
   public SelectList DeviceTypeList { get; set; }
   public int SelectedDeviceType { get; set; }

   public EditDeviceViewModel(Device device, IEnumerable<DeviceType> DeviceTypes)
   {
      ...
      DeviceTypeList = new SelectList(DeviceTypes.OrderBy(t => t.Type), 
                                      "ID", 
                                      "Type", 
                                      device.DeviceType.ID);
      SelectedDeviceType = device.DeviceType.ID;
   }
}

Then in my view I am creating a drop down using the Html helper

@Html.DropDownListFor(model => model.SelectedDeviceType, 
                      Model.DeviceTypeList, 
                      new { id = "devicetypelist" })

When the view is rendered开发者_如何学运维, the value I selected when initialising the SelectList isn't selected. What am I doing wrong?

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DropDown list will use the value of SelectedDeviceType property as the selected value. What you can do is set the property value when you construct the model

public class EditDeviceViewModel
{
   public SelectList DeviceTypeList { get; set; }
   public int SelectedDeviceType { get; set; }

   public EditDeviceViewModel(Device device, IEnumerable<DeviceType> DeviceTypes)
   {
      ...
      DeviceTypeList = new SelectList(DeviceTypes.OrderBy(t => t.Type), 
                                      "ID", 
                                      "Type");

      SelectedDeviceType = device.DeviceType.ID;
      ...
   }
}

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THe first argument to DropDownListFor must be the variable that holds your selected value. Are you setting SelectedDeviceType anywhere?