Loop through attribute of a class and get a count of how many properties that are not null

问题

I was wondering if there was a simpler way to do something like this?

    public int NonNullPropertiesCount(object entity)
    {
        if (entity == null) throw new ArgumentNullException("A null object was passed in");


        int nonNullPropertiesCount = 0;
        Type entityType = entity.GetType();

        foreach (var property in entityType.GetProperties())
        {
            if (property.GetValue(entity, null) != null)
                nonNullPropertiesCount = nonNullPropertiesCount+ 1;
        }


        return nonNullPropertiesCount;
    }

回答1:

How about:

public int NonNullPropertiesCount(object entity)
{
    return entity.GetType()
                 .GetProperties()
                 .Select(x => x.GetValue(entity, null))
                 .Count(v => v != null);
}

(Other answers have combined the "fetch the property value" and "test the result for null". Obviously that will work - I just like to separate the two bits out a bit more. It's up to you, of course :)

回答2:

Type entityType = entity.GetType();

int count = entityType.GetProperties().Count(p => p.GetValue(p, null) != null);

回答3:

Your code is OK, can suggest using Linq

entity
  .GetProperties()
  .Count(x=>x.CanRead && x.GetProperty(entity, null) != null)

And don't forget to add condition, that property has getter.

来源：https://stackoverflow.com/questions/4328411/loop-through-attribute-of-a-class-and-get-a-count-of-how-many-properties-that-ar