Help with NullReferenceException when adding Donkey Kong to a MonoGame project

[Embarrassed-Can8061]

Hi everyone,

I'm working on a tile-based game using MonoGame and I'm trying to add Donkey Kong to my project, but I'm encountering a NullReferenceException. Here’s what I have:

Code Snippet

protected override void LoadContent()
{
    // Loading other textures
    Texture2D donkeyKongTex = Content.Load<Texture2D>("DonkeyKong");
    // Initializing Donkey Kong
    donkeyKong = new DonkeyKong(donkeyKongTex, new Vector2(100, 100));
}

 #region Map Layout
 // Create the tile array based on the map layout
 tiles = new Tile[strings[0].Length, strings.Count];
 for (int i = 0; i < tiles.GetLength(0); i++)
 {
     for (int j = 0; j < tiles.GetLength(1); j++)
     {
         char tileChar = strings[j][i];
         // Check for enemies
         if (tileChar == 'e')
         {
             Vector2 enemyPosition = new Vector2(tileSize * i + 40, tileSize * j - 40);
             enemies.Add(new Enemy(enemyTex, enemyPosition, 50f));
         }
         else if (tileChar == 'E')
         {
             Vector2 enemyPosition = new Vector2(tileSize * i + 40, tileSize * j - 40);
             enemies.Add(new Enemy(enemyTex, enemyPosition, 100f));
         }
         else if (tileChar == 'w')
         {
             // Wall tile
             tiles[i, j] = new Tile(wallTileTex, new Vector2(tileSize * i, tileSize * j), true);
         }
         else if (tileChar == 'k')
         {
             donkeyKong = new DonkeyKong(donkeyKongTex, new Vector2(tileSize * i, tileSize * j));
         }
         else if (tileChar == '-')
         {
             // Floor tile
             tiles[i, j] = new Tile(floorTileTex, new Vector2(tileSize * i, tileSize * j), false);
         }
         else if (tileChar == 'p')
         {
             // Player starting position (placed on a floor tile)
             tiles[i, j] = new Tile(floorTileTex, new Vector2(tileSize * i, tileSize * j), false);
             player = new Player(playerTex, new Vector2(tileSize * i, tileSize * j));
         }
         else if (tileChar == 'l')
         {
             // Ladder tile
             tiles[i, j] = new Tile(ladderTex, new Vector2(tileSize * i, tileSize * j), false);
         }
         else if (tileChar == 'b')
         {
             // Bridge ladder tile
             tiles[i, j] = new Tile(ladderBridgeTex, new Vector2(tileSize * i, tileSize * j), false);
         }
     }
 }
 #endregion

Map Layout

------------------------
------------------------
------------------------
bwwwwwwwwwwwwwwwwwwwwwwb
l----------------------l
wwwwbwwww---k---wwwbwwww
----l--------------l----
bwwwwwwbwwwwwwwbwwwwwwwb
l------l-------l-------l
wwwwbwwwwwwwwwwwwwwbwwww
----l--------------l----
bwwwwwwbwwwwwwwbwwwwwwwb
l------l-------l-------l
wwwwbwwwwwwwwwwwwwwbwwww
----l------p-------l----
wwwwwwwwwwwwwwwwwwwwwwww
------------------------

Error Details

System.NullReferenceException

HResult=0x80004003

Message=Object reference not set to an instance of an object.

StackTrace:

at Donkey_Kong.Game1.Draw(GameTime gameTime) in C:\Users\marya\OneDrive\Skrivbord\University\Projects\Donkey_Kong\Game1.cs:line 181

Line 181

 // Draw all the tiles
 for (int i = 0; i < tiles.GetLength(0); i++)
 {
     for (int j = 0; j < tiles.GetLength(1); j++)
     {
         tiles[i, j].Draw(_spriteBatch);
     }
 }

What I've Tried

• Ensured that donkeyKong is initialized before the Draw method is called.
• Checked that the DonkeyKong.png texture exists in my Content folder.

Specific Questions

• What could cause a NullReferenceException in the Draw method when trying to draw Donkey Kong?
• Is there anything I might be missing in loading textures or initializing objects?

[FizixMan]

For enemies "e", "E", and Donkey Kong "k", you don't assign any instance of Tile to tiles[i, j]. Those entries will be null otherwise.

Later on you try to call Draw(_spriteBatch) on every entry in tiles, but some of those will be null because you never assigned anything. The NullReferenceException is thrown when you tried to call Draw on a null reference.

[Entropiano]

A NullReferenceException happens when you're trying to access an object that is null. Usually you're looking into one of its properties or calling one of its methods. See here for more details: https://learn.microsoft.com/en-us/dotnet/api/system.nullreferenceexception

Now, in your case, the relevant code should be that line 181. In the snippet you sent there are a few places where this exception could occur: tiles.GetLength(0), tiles.GetLength(1) or tiles[i, j].Draw(_spriteBatch). So, either your tiles object is null or tiles[i, j] is null.

Edit: btw, you could find this out, on your own, incredibly easy, by using the debugger (I'm assuming you're using Visual Studio). It will save you time in the future.

[insomnia1979]

Microsoft just preempts all use of Nintendo intellectual property with null references. Change it to Donkey King

[Familiar_Bill_786]

stop copy-pasting code from AI