Null reference on static class property

Question

I have a static class:

public static class Options
{
    public static MiscSettings MiscSettings;
    public static Units Units;
}

My definitions for the two property classes looks like this:

[Serializable]
public class Units
{
    public LengthUnit LengthUnit { get; set; } = LengthUnit.Millimeter;
    public VolumeUnit VolumeUnit { get; set; } = VolumeUnit.CubicCentimeter;
}

[Serializable]
public class MiscSettings
{
    public bool OutputDebugging { get; set; } = false;
}

When I do:

Options.Units = OptionsData.Units;
Options.MiscSettings.OutputDebugging = false;

The first line executes ok. The second gives me a NullReference Exception. The property Options.MiscSettings is null. The next error is Object not set to an instance of an object.

I've tried renaming everything, changing order of the properties. I also tried moving the property OutputDebugging to the Units class and that worked just fine.

Any help would be appreciated.

Answer 1

Just because a field is static doesn't mean you don't have to initialize it. Here, MiscSettings is never initialized, so it's null, and when you try to set its OutputDebugging you get the aforementioned NullReferenceException.

One easy way to to set OutputDebuggin would be to initialize MiscSettings with an object initializer:

Options.MiscSettings = new MiscSettings
{
    OutputDebugging = false;
}

Answer 2

try this

if(Options.MiscSettings==null) Options.MiscSettings=new MiscSettings();
Options.MiscSettings.OutputDebugging = false;

Answer 3

When you are creating a class object, you need to make sure to initialize the variables you will use. The MiscSettings variable is not set, therefore you are getting a NullReferenceException.Options.MiscSettings = new MiscSettings();