C# to Java object wrapper

JavaHolder.cs

using System;

public class JavaHolder : Java.Lang.Object
{
    public readonly object Instance;

    public JavaHolder(object instance)
    {
        Instance = instance;
    }
}

ObjectExtensions.cs

using System;

public static class ObjectExtensions
{
    public static TObject ToNetObject<TObject>(this Java.Lang.Object value)
    {
        if (value == null)
            return default(TObject);

        if (!(value is JavaHolder))
            throw new InvalidOperationException("Unable to convert to .NET object. Only Java.Lang.Object created with .ToJavaObject() can be converted.");

        TObject returnVal;
        try { returnVal = (TObject) ((JavaHolder) value).Instance; }
        finally { value.Dispose(); }
        return returnVal;
    }

    public static Java.Lang.Object ToJavaObject<TObject>(this TObject value)
    {
        if (Equals(value, default(TObject)) && !typeof(TObject).IsValueType)
            return null;

        var holder = new JavaHolder(value);

        return holder;
    }
}