Question

could someone help me with the linq statement,

this is what i have so far

public class Categories : ObservableCollection<Category>
{ 
    public Categories() { } 

    public int getBoardIndex(int BoardId)
    {
        return (from category in this
                from board in category.CategoryBoards
                where board.BoardId == BoardId
                select IndexOf(board)
                    );
    }
}

board is an item in category and when i pass a bordId ( which is not an index ) it must search for that BoardId in all boards in each category and then return the Index Of that board

how do i do it using Linq?

Thank you so much for all your help!!!

Answer 1

EDIT

This is a much simpler version of the same thing:

public int getBoardIndex(int BoardId)
{
    return (from category in this
            from board in category.CategoryBoards
            where board.BoardId == BoardId
            select category.CategoryBoards.ToList().IndexOf(board)).FirstOrDefault();
}

Original Version

To get the index of the first matching Board in its own Category, first find the Category, then get the index of the board:

public int getBoardIndex(int BoardId)
{

    var categoryBoard = (from category in this
                         from board in category.CategoryBoards
                         where board.BoardId == BoardId
                         select new {category, board}).FirstOrDefault();
    return categoryBoard.category.CategoryBoards.IndexOf(categoryBoard.board);
}

To get the index of the first matching Board in a flattened collection amongst all of the Categories, then @Dan Tao has the best answer.