Bitmap() results in compile error for invalid parameter

I am using VS2015 Community under Windows 8.1. I am working through a tutorial on building a level editor for a game. The tutorial was originally written for XNA. The tutorial uses Windows Forms to display the editor. All has worked until I wrote the code (following the tutorial) to import the tileset. Below is the code for the method. When I execute the app I get a debug message at the point indicated by the **. This is where the tiles are read into the method. I have been trying to find a solution. I researched the Bitmap class and the syntax I believe is correct. If anyone has any suggestions or corrections please let me know.

private void LoadImageList()
string filepath = Application.StartupPath +
Bitmap tileSheet = new Bitmap(filepath);
int tilecount = 0;
for (int y = 0; y < tileSheet.Height / TileMap.TileHeight; y++)
for (int x = 0; x < tileSheet.Width / TileMap.TileWidth; x++)
Bitmap newBitmap = tileSheet.Clone(new
x * TileMap.TileWidth,
y * TileMap.TileHeight,

            string itemName = "";
            if (tilecount == 0)
                itemName = "Empty";
            if (tilecount == 1)
                itemName = "White";
                ListViewItem(itemName, tilecount++));