Trouble choosing a random spawn location in 2D tile based platformer

Hi everyone,

I'm in the middle of creating a 2D tile based game. Just a minor problem I am encountering: I have a CSV file which is read into an array for the level map - this all works fine. I am have a second CSV file with the same number of rows/columns which holds numbers to represent spawn points for weapon power ups. I want the power ups to randomly appear, but only at one of a few specific locations, basically at one of the tiles where the value is '2'.

The problem is I am trying to randomly pick a tile by using a do ... while loop, which is proving to be very costing, slowing the game to a halt until the loop finds a valid tile. I'm not very good at explaining this but hopefully you understand what I mean, anyway heres the code (bear in mind this is my first time programming a game so my code may be somewhat novice :-):

From the top:

//represents the number of rows and columns in the csv file/map
private static int MapTileRow = 20;
private static int MapTileColumn = 26;

Later in the code:

bool SpawnPointFound = false;
int x, y;

do
{
Random RandomTile = new Random();
x = RandomTile.Next(MapTileRow);
y = RandomTile.Next(MapTileColumn);

if (WeaponSpawnArray[x, y] == 2)
{ SpawnPointFound = true;}
}
while (!SpawnPointFound);

Are there any more efficient ways of doing this I was thinking perhaps of, when reading in the CSV file, storing the co-ordinates of each '2' tile in another array, and then just picking one of these coordinates from the array at random, but I couldn't think of a way to implement it.

Many thanks in advance for any help.

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Trouble choosing a random spawn location in 2D tile based platformer

Airmax
Never mind, I found that putting the Random RandomTile = new Random(); outside the do loop stopped the pause. My bad! Still, if there are any more efficient ways to do this I'd be very willing to hear.
13thGhost

Why not just keep a HashTable of spawn points and generate the random number based on the number of elements in the HashTable

        private Hashtable spawnPoints;    //filled elsewhere
        private Random rnd = new Random();

        private Vector2 GetSpawnPoint()
        {
            Vector2 pt;

            int index = rnd.Next(0, spawnPoints.Count);

            pt = new Vector2(((Vector2)spawnPoints[index]).X, ((Vector2)spawnPoints[index]).Y);

            return pt;
        }

Using a Hashtable would allow you to do lookups using the ContainsValue method. You could use a List<Vector2> object as well if you don't need to do lookups.
Trouble choosing a random spawn location in 2D tile based platformer

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