C#: IsDisposed() Checks to see if an object is disposed.

ObjectExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

public static class ObjectExtensions
{
    public static bool IsDisposed(this IDisposable obj)
    {
        /*
         TIM C: This hacky code is because MSFT does not provide a standard way to interrogate if an object is disposed or not. 
            I wrote this based upon streams, but it should work for many other types of MSFT objects (maybe).
        */
        if (obj == null) { return true; }

        var objType = obj.GetType();
        //var foo = new System.IO.BufferedStream();

        // the _disposed pattern should catch a lot of msft objects.... hopefully
        var isDisposedField = objType.GetField("_disposed", BindingFlags.NonPublic | BindingFlags.Instance) ??
            objType.GetField("disposed", BindingFlags.NonPublic | BindingFlags.Instance);

        if (isDisposedField != null) { return Convert.ToBoolean(isDisposedField.GetValue(obj)); }

        isDisposedField = objType.GetField("_isOpen", BindingFlags.NonPublic | BindingFlags.Instance);

        if (isDisposedField != null) { return !Convert.ToBoolean(isDisposedField.GetValue(obj)); }

        // System.IO.FileStream
        var strategyField = objType.GetField("_strategy", BindingFlags.NonPublic | BindingFlags.Instance);
        if (strategyField != null)
        {
            var strategy = strategyField.GetValue(obj);
            var isClosedField = strategy.GetType().GetProperty("IsClosed", BindingFlags.NonPublic | BindingFlags.Instance);
            if (isClosedField != null) { return Convert.ToBoolean(isClosedField.GetValue(strategy)); }
        }

        // other streams that use this pattern to determine if they are disposed
        if (obj is Stream stream) { return !stream.CanRead && !stream.CanWrite; }

        return false;
    }
}

Sometimes, for whatever reason you need to check if an object is disposed. Well, there is no built in way to do that. So this mess was written against the Stream objects. The _disposed should catch a LOT of msft objects, but I am betting there are even weirder patterns out there.

Good luck using this code, YMMV