System.NullReferenceException in monogame

Question

I have some problems with creating a soundmanager.cs in monogame in c#. There is a System.NullReferenceException in my add function. Here is the important part of my SoundManager

public sealed class SoundManager
{
    public static Dictionary<string, SoundEffect> mSoundEffects;
    public static ContentManager mContentMgr;

    public SoundManager(ContentManager contentManager)
    {
        mContentMgr = contentManager;
        mSoundEffects = new Dictionary<string, SoundEffect>();

    }

    public static void AddSoundEffect(string soundName)
    {
        if (!mSoundEffects.ContainsKey(soundName))  //System.NullReferenceException error mSoundeffects = null, soundName = "energyCircleSound"
        {
            mSoundEffects.Add(soundName, mContentMgr.Load<SoundEffect>(soundName));
        }
    }
}

In another class I want to load the sound with the following code.

 public static SoundEffect mEffectSound;
 private static SoundEffect energyCircle;
 public override void LoadAssets()
    {
        // Load sound effects

        SoundManager.AddSoundEffect("energyCircleSound");


        mEffectSound = Soundmanager.mSoundEffects["energyCircleSound"];
    }
    [...]
    private void CastEnergyCircle(Vector2 position)
    {
        if (AreaOfEffect.Cooldown > 0)
        {
            // Nothing happens yet if cooldown hasn't expired
            return;
        }
        AreaOfEffect energyCircle = new AreaOfEffect(50, 50, 2000, 500, position, mEffectTexture, mEffectSound);
        mEffects.Add(energyCircle);
        energyCircle.Sound.Play();
        //SoundManager.PlayEnergyCircle();
        energyCircle.DealDamage(mTargets);
        RemoveDeadTargets();
    }

There is no problem with areofEffects. Everything works perfect without the sound manager. I don't understand this error. I think mSoundeffects should not be null, because i load something in it with LoadAsset(). Could anybody help me, please?

Answer 1

Your constructor is an instance constructor and likely never called, that is why your static method fails when it relies on instance methods being called previously.

I don't know whether you want to use this as a static class or an instance. Either way, decide for one and go with it. Mixing it can be very confusing.