Element is already the child of another element - WinRT

Question

I need to develop a structure similar to Windows 8 Start screen. I have a method which I call to populate my RecordTile. Method is like,

public static void fnShowTiles(List<RecordTile> objList, Grid objGrid) // objGrid is root Grid which holds this structure
    {
        try
        {
            // copy the list into local variable
            List<RecordTile> objListOfTiles = objList.ToList<RecordTile>();

            int nColumnsCount = -1;
            objGrid.Children.Clear();
            objGrid.ColumnDefinitions.Clear();
            StackPanel objPanel = new StackPanel();

            int nOriginalListCount = objListOfTiles.Count;
            int nRowsToRender = 4;

            while (objListOfTiles.Count > 0)
            {
                // add new column to the grid
                objGrid.ColumnDefinitions.Add(new ColumnDefinition());
                nColumnsCount += 1;

                // add new stackpanel to newly added column
                objPanel = new StackPanel();

                objGrid.Children.Add(objPanel);
                Grid.SetColumn(objPanel, nColumnsCount);

                // add elements to stackpanel
                int i = 0;
                while (i < nRowsToRender)
                {
                    if (objListOfTiles.Count > 0)
                    {
                        // add first element and remove it from list, so that next element will be first
                        RecordTile tile = objListOfTiles.First();
                        objPanel.Children.Add(tile); // exception occurs here
                        objListOfTiles.Remove(tile);
                        i++;
                    }
                    else
                    {
                        // if while adding elements, list finishes, then break the loop
                        break;
                    }
                }
            }
    }

This is working fine for the first load. I have a SearchBox on the same page where these tiles are getting loaded. When I filter the Tiles (based on search string) and pass new list of tiles to the function, it throws exception.

I went through many posts. They suggested to remove element from its parent. I'm clearing the children of grid every time. What must be going wrong?

Answer 1

As @Rawling suggested, clearing the Tiles from StackPanel before objGrid.Children.Clear(); was the solution. Added following code before that statement and it worked like a charm.

foreach (StackPanel panel in objGrid.Children)
{
    panel.Children.Clear();
}