C＃如何将对象内的所有空列表转换为null

Question

First of all, i'm aware of the popular advice that you should avoid returning empty lists at all. But as of now, due to a myriad of reasons, i'm met with no other choice but to do just that.

What i'm asking is how do I iterate through the properties of an object (probably through Reflection ), take whatever lists I may find and check if it's empty. If so, then turn it into null , otherwise, leave it be.

I'm stuck with the following code, which includes somewhat of a try with Reflection :

private static void IfEmptyListThenNull<T>(T myObject)
{
    foreach (PropertyInfo propertyInfo in myObject.GetType().GetProperties())
    {
        if (propertyInfo.PropertyType.IsGenericType && propertyInfo.PropertyType.GetGenericTypeDefinition() == typeof(List<>))
        {
            //How to know if the list i'm checking is empty, and set its value to null
        }
    }
}

Answer 1

This should work for you, just use GetValue method and cast value to IList , then check for emptiness and set this value via SetValue to null .

private static void IfEmptyListThenNull<T>(T myObject)
        {
            foreach (PropertyInfo propertyInfo in myObject.GetType().GetProperties())
            {
                if (propertyInfo.PropertyType.IsGenericType && propertyInfo.PropertyType.GetGenericTypeDefinition() == typeof(List<>))
                {
                    if (((IList)propertyInfo.GetValue(myObject, null)).Count == 0)
                    {
                        propertyInfo.SetValue(myObject, null);
                    }
                }
            }
        }