How to fix System.NullReferenceException: Object reference not set to an instance of an object

Question

EDIT: This issue is resolved, good thanks to Reniuz for his 5 hours of work and research of this issue, thank's everyone.

NullReferenceException: Object reference not set to an instance of an object. on the following code and I've searched and searched and pulled my hair out for over 7-8 hours now trying to fix it.

private void buttonAddEffect_Click_1(object sender, EventArgs e)
{
    EffectSelectorForm effectSelectorForm = new EffectSelectorForm(Effects);
    if (effectSelectorForm.ShowDialog(this) == DialogResult.OK)
    {
        // create a new instance of the selected effect as we may want multiple copies of one effect
        Effect effect = (Effect)Activator.CreateInstance(effectSelectorForm.SelectedEffect.GetType());
        audioGraph.AddEffect(effect);
        int index = checkedListBox1.Items.Add(effect, true);
        checkedListBox1.SelectedIndex = index;
    }
    //MessageBox.Show(String.Format("I have {0} effects", Effects.Count));
}

Error is on the line: EffectSelectorForm effectSelectorForm = new EffectSelectorForm(Effects);

the class:

namespace WindowsFormsApplication13
{
    public partial class EffectSelectorForm : Form
    {
        public EffectSelectorForm(ICollection<Effect> effects)
        {
            InitializeComponent();
            listBoxEffects.DisplayMember = "Name";
            listBoxEffects.DataSource = effects;
        }

        private void buttonOK_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.OK;
            this.Close();
        }

        public Effect SelectedEffect
        {
            get
            {
                return (Effect)listBoxEffects.SelectedItem;
            }
        }

        private void listBoxEffects_DoubleClick(object sender, EventArgs e)
        {
            buttonOK_Click(sender, e);
        }

What this is supposed to do is when the effectSelectorForm loads it should make a list of all the voice changer options but it does not do that.... it loads nothing on it, I got this code from another form for changing voice in Skype and re-wrote about 400 lines of code for it to work in my app but now I have this issue and I'm not giving up with all the effort I've put in so far. If it loaded on the other project why not in this one? I've went over code for hours over and over thinking im missing something but no.

Any help would be fantastic.

Stack

See the end of this message for details on invoking 
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at WindowsFormsApplication13.pwn4g3.buttonAddEffect_Click_1(Object sender, EventArgs e) in F:\Users\Tom\Desktop\New folder\New folder (2)\TestApp\pwn4g3\PWN4G3\MainForm2.cs:line 1758
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Effect.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace JSNet
{    

    public abstract class Effect
    {
        private List<Slider> sliders;
        public float SampleRate { get; set; }
        public float Tempo { get; set; }
        public bool Enabled { get; set; }

        public Effect()
        {
            sliders = new List<Slider>();
            Enabled = true;
            Tempo = 120;
            SampleRate = 44100;
        }

        public IList<Slider> Sliders { get { return sliders; } }

        public Slider AddSlider(float defaultValue, float minimum, float maximum, float increment, string description)
        {
            Slider slider = new Slider(defaultValue, minimum, maximum, increment, description);
            sliders.Add(slider);
            return slider;
        }

        public abstract string Name { get; }

        // helper base methods
        // these are primarily to enable derived classes to use a similar
        // syntax to JS effects
        protected float slider1 { get { return sliders[0].Value; } }
        protected float slider2 { get { return sliders[1].Value; } }
        protected float slider3 { get { return sliders[2].Value; } }
        protected float slider4 { get { return sliders[3].Value; } }
        protected float slider5 { get { return sliders[4].Value; } }
        protected float slider6 { get { return sliders[5].Value; } }
        protected float slider7 { get { return sliders[6].Value; } }
        protected float slider8 { get { return sliders[7].Value; } }
        protected float min(float a, float b) { return Math.Min(a, b); }
        protected float max(float a, float b) { return Math.Max(a, b); }
        protected float abs(float a) { return Math.Abs(a); }
        protected float exp(float a) { return (float)Math.Exp(a); }
        protected float sqrt(float a) { return (float)Math.Sqrt(a); }
        protected float sin(float a) { return (float)Math.Sin(a); }
        protected float tan(float a) { return (float)Math.Tan(a); }
        protected float cos(float a) { return (float)Math.Cos(a); }
        protected float pow(float a, float b) { return (float)Math.Pow(a, b); }
        protected float sign(float a) { return Math.Sign(a); }
        protected float log(float a) { return (float)Math.Log(a); }
        protected float PI { get { return (float)Math.PI; } }

        protected void convolve_c(float[] buffer1, int offset1, float[] buffer2, int offset2, int count)
        {
            for (int i = 0; i < count * 2; i += 2)
            {
                float r = buffer1[offset1 + i];
                float im = buffer1[offset1 + i + 1];
                float cr = buffer2[offset2 + i];
                float ci = buffer2[offset2 + i + 1];
                buffer1[offset1 + i] = r * cr - im * ci;
                buffer1[offset1 + i + 1] = r * ci + im * cr;
            }
        }


        public virtual void Init()
        {
        }


        public abstract void Slider();


        public virtual void Block(int samplesblock)
        { 
        }


        public abstract void Sample(ref float spl0, ref float spl1);

        public override string ToString()
        {
            return Name;
        }
    }
}

The stack trace would be helpful. Are you sure there are not fields in Effect that are null that when the DataSource is set and processed are causing the null? — Andrew T Finnell
– Andrew T Finnell, Commented Apr 6, 2012 at 12:08
> Stack trace added, and it's if I press okay I get the error, but I guess it's because their is nothing in the listbox and its returning null.. in that case I need to find why their is nothing in the list. — iKonroi
– iKonroi, Commented Apr 6, 2012 at 12:11
cant you debug and see what do you have in Effects variable, which is passed to form? — Renatas M.
– Renatas M., Commented Apr 6, 2012 at 12:12
That line should not throw a NullReferenceException. If Effects is null, it should throw an ArgumentNullException. — Kendall Frey
– Kendall Frey, Commented Apr 6, 2012 at 12:14

walther · Accepted Answer · 2012-04-06 17:56:52Z

4

If the problem is 100% here

EffectSelectorForm effectSelectorForm = new EffectSelectorForm(Effects);

There's only one possible explanation: property/variable "Effects" is not initialized properly... Debug your code to see what you pass to your objects.

EDIT after several hours

There were some problems:

MEF attribute [Import] didn't work as expected, so we replaced it for the time being with a manually populated List<>. While the collection was null, it was causing exceptions later in the code, when the method tried to get the type of the selected item and there was none.
several event handlers weren't wired up to control events

Some problems are still present, but I believe OP's original problem has been fixed. Other problems are not related to this one.

edited Apr 6, 2012 at 17:56

answered Apr 6, 2012 at 12:12

walther

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11 Comments

Andrew T Finnell Over a year ago

It has to do with the objects in that list. Because you can set a DataSource to null just fine. If Effects was null it would just be an empty list and he wouldnt be able to select anything. So it has to be the objects in this list. Sometimes the magic in .NET is great, other times it makes debugging impossible.

iKonroi Over a year ago

I think it because I'm pressing okay when it's null.. and like I said if that's the issue then I am still jammed on the issue that I cannot get it to load effects. Sorry I'm a little new to this. I did debug and not sure how it helps to find error.

iKonroi Over a year ago

@AndrewFinell it does debug, yes.. but once I open that listbox and press okay it break's debugging now.. And I understand why, because it's null.. But now I need to work on why the listbox is not having content added to it.

Renatas M. Over a year ago

@iKonroi I really suggest you to read this article: Mastering Debugging

walther Over a year ago

@AndrewFinnell, yes, that's true. However, by saying "not initialized properly" I meant it somewhat more general, not necessarily that the list itself is null.

|

lcryder · Accepted Answer · 2012-04-06 14:21:08Z

1

During debug, break on all exceptions thrown. Debug->Exceptions

Check all 'Thrown' exceptions. F5, the code will stop on the offending line.

answered Apr 6, 2012 at 14:21

lcryder

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Comments

Edmett · Accepted Answer · 2012-11-17 00:57:35Z

0

I had the same problem but it only occurred on the published website on Godaddy. It was no problem in my local host.

The error came from an aspx.cs (code behind file) where I tried to assign a value to a label. It appeared that from within the code behind, that the label Text appears to be null. So all I did with change all my Label Text properties in the ASPX file from Text="" to Text=" ".

The problem disappeared. I don’t know why the error happens from the hosted version but not on my localhost and don’t have time to figure out why. But it works fine now.

answered Nov 17, 2012 at 0:57

Edmett

111 bronze badge

Comments

David Buck · Accepted Answer · 2020-06-18 12:53:03Z

I was getting this same error, but for me this was due to a method in a base class (in Project A) having the output type changed from a non-void type to void. A child class existed in Project B (which I didn't want used and had marked obsolete) that I missed when performing this update and hence started throwing this error.

1>CSC : error CS8104: An error occurred while writing the output file: System.NullReferenceException: Object reference not set to an instance of an object.

Original Code:

[Obsolete("Calling this method will throw an error")]
public override CompletionStatus Run()
{
    throw new CustomException("Run process not supported.");
}

Revised Code:

[Obsolete("Calling this method will throw an error")]
public override void Run()
{
    throw new CustomException("Run process not supported.");
}

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