help family instance error

[Anonymous]

i get the following error when trying to run following code 

Object reference not set to an instance of an object.

please help

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Autodesk.Revit.DB;
using Autodesk.Revit.DB.Electrical;
using Autodesk.Revit.UI;
using Autodesk.Revit.UI.Selection;
using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB.Architecture;
using Autodesk.Revit.DB.Structure;

[TransactionAttribute(TransactionMode.Manual)]
[RegenerationAttribute(RegenerationOption.Manual)]
public class LightingDistribution : IExternalCommand
{
public List<Face> m_faceList = new List<Face>();
public Result Execute(
ExternalCommandData commandData,
ref string message,
ElementSet elements)
{
UIApplication uiApp = commandData.Application;
Document doc = uiApp.ActiveUIDocument.Document;

try
{
// Reference pickedRef = null;
Reference pickedLit = null;
Selection sel = uiApp.ActiveUIDocument.Selection;

// Pick a light fixture
LightPickFilter LselFilter = new LightPickFilter();
pickedLit = sel.PickObject(ObjectType.Element, LselFilter,
"Please select Lighting Fixture");
Element Lelem = pickedLit.Element;

// Ask the user to pick target rooms
RoomPickFilter roomPickFilter = new RoomPickFilter();
IList<Reference> rooms =
sel.PickObjects(
ObjectType.Element,
roomPickFilter,
"Select target rooms for duplicate Lights");

FamilyInstance inst = Lelem as FamilyInstance;

// Get light symbol name

FamilySymbol Lt = GetInfo_FamilyInstance_Symbol(inst);

pickedLit = sel.PickObject(ObjectType.Element,
"Please select ceilingssssssssssss");

Element Lelem1 = pickedLit.Element;

object obj = Lelem1 as object;
Solid soli = obj as Solid;
FaceArray faces = soli.Faces;

int ii = 0;
foreach (Face tempFace in faces)
{


m_faceList.Add(tempFace);
ii++;

}

// Place light in each of the rooms transaction
Transaction trans = new Transaction(doc);
trans.Start("Lab");
PlaceLightInRooms(doc, rooms, m_faceList, Lt);
trans.Commit();
}

// If user right-clicks or presess Esc button,
// handle the exception
catch (Autodesk.Revit.Exceptions.OperationCanceledException)
{
return Result.Cancelled;
}
// Catch other errors
catch (Exception ex)
{
message = ex.Message;
return Result.Failed;
}

return Result.Succeeded;
}

/// <summary>
/// Return the center of an element based on its BoundingBox
/// </summary>
public XYZ GetElementCenter(Element elem) //required for get room center
{
BoundingBoxXYZ bounding = elem.get_BoundingBox(null);
XYZ center = (bounding.Max + bounding.Min) * 0.5;
return center;
}

public FamilySymbol Getsymbol(Element LTelem)
{
FamilySymbol lit = LTelem as FamilySymbol;
return lit;
}

public FamilySymbol GetInfo_FamilyInstance_Symbol(FamilyInstance familyInstance)
{
FamilySymbol lit = familyInstance.Symbol;
return lit as FamilySymbol;
}

/// Return a room's center point coordinates.

public XYZ GetRoomCenter(Room room)
{
// Get the room center point.
XYZ boundCenter = GetElementCenter(room);
return boundCenter;
}

//Method
public void PlaceLightInRooms(
Document doc,
IList<Reference> rooms, List<Face> m_faceLis, FamilySymbol LT)
{
foreach (Reference r in rooms)
{
Room roomTarget = doc.get_Element(r.Element.Id) as Room;
if (roomTarget != null)
{
XYZ dir = new Autodesk.Revit.DB.XYZ(1.0f, 0f, 0f);

Face face = m_faceLis[1];
XYZ roomCenter = GetRoomCenter(roomTarget);
FamilyInstance newlit = doc.Create.NewFamilyInstance(face, roomCenter, dir, LT);

}
}
}
}

/// <summary>
/// Filter to constrain picking to Light fixtures
/// </summary>
public class LightPickFilter : ISelectionFilter
{
public bool AllowElement(Element e)
{
return (e.Category.Id.IntegerValue.Equals(
(int)BuiltInCategory.OST_LightingFixtures));
}
public bool AllowReference(Reference r, XYZ p)
{
return false;
}
}

/// <summary>
/// Filter to constrain picking to rooms
/// </summary>
public class RoomPickFilter : ISelectionFilter
{
public bool AllowElement(Element e)
{
return (e.Category.Id.IntegerValue.Equals(
(int)BuiltInCategory.OST_Rooms));
}

public bool AllowReference(Reference r, XYZ p)
{
return false;
}
}

[ollikat]

If you could please provide a little bit more information about the place where the exception came form. The full stack trace would be best, but please tell us at least the line where it came from.

But basically you have null pointer somewhere...maybe some function failed to return the pointer for you or something similar.