C# Reflection, setting new instance of a null property

Question

I've writing a small method whose sole purpose is to check if a property is null for a given class. If the property is null, then create a new instance of it. I'm getting stuck on part where I'm actually setting a value:

  public static void CheckIfPropertyIsNull<TEntity>(SomeBusinessEntity someBusinessEntity) where TEntity : new()
    {
        var properties = typeof(SomeBusinessEntity).GetProperties();

        foreach (PropertyInfo propertyInfo in properties)
        {
            Type currentType = propertyInfo.PropertyType;
            if (currentType == typeof(TEntity))
            {
                var propertyData = propertyInfo.GetValue(someBusinessEntity, null);
                if (propertyData == null)

                {
                    object instance = Activator.CreateInstance(typeof(TEntity));

                    // And then?
                    //propertyInfo.SetValue(null, instance);

                    return;
                }
            }
        }
    }

I try to use the SetValue() method but with no luck.

You've gone to the bother of requesting from the generics system that any type you're supplied has a parameterless constructor - so why not just new TEntity() rather than Activator.CreateInstance(...)? — Damien_The_Unbeliever
– Damien_The_Unbeliever, Commented Jul 29, 2016 at 10:49
I had some thought process and was just doodling around with the code. I was using new TEntity() before. — JL-ConcepT
– JL-ConcepT, Commented Jul 29, 2016 at 10:52

Patrick Hofman · Accepted Answer · 2016-07-29 10:47:48Z

5

In your SetValue you still have to give the instance of the owner of the property: someBusinessEntity.

object instance = new TEntity();

// And then
propertyInfo.SetValue(someBusinessEntity, instance);

Note that your logic seems odd to me. You are using a generic type to set all properties. Why not use the type of the property?

answered Jul 29, 2016 at 10:47

Patrick Hofman

158k23 gold badges270 silver badges343 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

JL-ConcepT Over a year ago

Thank you Patrick. It works. Im quite new to reflection and don't quite understand your last part.

Collectives™ on Stack Overflow

C# Reflection, setting new instance of a null property

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related