sizeof - Estimate the size of a managed instance

GetSizeOfObject.cs

public static int GetSizeOfObject(object obj, StringBuilder sb = null, int indent = 0, bool details = true)
{
    if (sb == null)
    {
        sb = new StringBuilder();
        sb.AppendLine("|Name |Type |Size(b)|");
        sb.AppendLine("|--- |--- |--- |");
    }

    if (indent == 0)
        sb.AppendLine($"**{obj.GetType().Name}**");

    int pointerSize = IntPtr.Size;
    int size = 0;
    Type type = obj.GetType();
    var info = type.GetFields(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic);
    foreach (var field in info)
    {
        if (field.FieldType.IsValueType)
        {
            if (field.FieldType.IsPrimitive)
            {
                var sz = Marshal.SizeOf(field.FieldType);
                sb.AppendLine($"|{new string('+', indent)}{field.Name}|{field.FieldType}|{sz}|");
                size += sz;
            }
            else
            {
                var sb2 = new StringBuilder();
                var sz = GetSizeOfObject(field.GetValue(obj), avgStringSize, sb2, indent + 1);
                sb.AppendLine($"|{new string('+', indent)}**{field.FieldType.Name}**|{field.FieldType}|{sz}|");
                if (details)
                    sb.Append(sb2.ToString());
                size += sz;
            }
        }
        else
        {
            size += pointerSize;
            sb.AppendLine($"|{new string('+', indent)}{field.Name} Reference|{field.FieldType}|{pointerSize}|");
        }
    }

    if (indent == 0)
    {
        sb.AppendLine($"\nTotal Size: {size}");
        Debug.Log(sb.ToString());
    }

    return size;
}

A quick and dirty way to try and see how much memory an instance is using. Prints a markdown dump of the breakdown.