C# - How do I get a list of classes with specific custom attributes having set their properties to a certain custom type? [duplicate]

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• What is a NullReferenceException, and how do I fix it? 33 answers

I have two classes...

  public enum MyType
            {
                type1,
                type2
            }


   [Sample(MyType.type2)]
    public class Person
    {

    }

    [Sample(type = MyType.type1)]
    public class People
    {

    }

and an attribute class ...

[AttributeUsage(AttributeTargets.All)]
      public class SampleAttribute : Attribute
{
    private MyType type { get; set; } = MyType.type1;
    public SampleAttribute(MyType _type)
    {
        type = _type;
    }
}

and following code into the Form_Load event...

var types = from t in Assembly.GetExecutingAssembly().GetTypes() select t;

            foreach (Type type in types)
            {
                if (type.GetCustomAttribute<SampleAttribute>().type == MyType.type1)
                {
                    listBox1.Items.Add(type.Name);
                }
            }

I wish to get a list of such classes for which I have set the custom attribute's property to type1

This code generates a run-time error saying..."object reference not set to an instance of an object"

Any suggestion? where and what I have missed to initialize? Thank you in advance.