序列化时忽略属性重写的XmlSerializer

我有一个复杂的图形,每个属性都有一个自定义属性。一旦有了对象,我就遍历属性,检查自定义属性,如有必要,添加要忽略的属性:

var ignoreAttribute = new XmlAttributes() {
    XmlIgnore = true
};
var overrides = new XmlAttributeOverrides();

var objType = obj.GetType();
var properties = objType.GetProperties();

foreach (var property in properties)
{
    var attrib = property.GetCustomAttribute<ExportLevelAttribute>();
    if (!attrib.Values.Contains(level))
    {
        try
        {
            var element = property.GetCustomAttribute<XmlElementAttribute>();
            var name = element?.ElementName == string.Empty ? property.Name : element.ElementName;

            overrides.Add(property.PropertyType, name, ignoreAttribute);
        }
        catch { }

        continue;
    }
}

using (var stream = new MemoryStream())
using (var writer = new StreamWriter(stream, new UTF8Encoding(false)))
{
    var xml = new XmlSerializer(typeof(MyRootObject), overrides);
    xml.Serialize(writer, obj);

    return Encoding.UTF8.GetString(stream.ToArray());
}

正在将属性添加到替代。但是,序列化时,那些设置为忽略的属性仍在序列化。