创建一个具有不同底层类型的Nullable对象数组？

Question

I have a number of nullable objects of different types (eg DateTime? , Guid? ) that I want to check for a value.

I'd like to avoid code like this:

return SomeGuid.HasValue || SomeBool.HasValue || SomeDateTime.HasValue

but it does not seem possible to create an array of Nullable<object> . I was hoping to do something like:

return new Nullable<object>[] { SomeGuid, SomeBool, SomeDateTime }.Any(o => o.HasValue);

Answer 1

object is nullable per definition.

So the following works:

Guid? guid = null;
bool? boolean = null;
DateTime? date = DateTime.Now;

var test = new object[] { guid, boolean, date }.Any(o => o != null);

Do note Nullable<T> requires T to be a struct , ie a value type (not a reference type). object is a reference type.

Answer 2

A little complicated, but you can wrap the nullable objects using a uniform interface, as follows:

interface INullableWrapper
{
    bool HasValue { get; }
    object Value { get; } // Careful: boxing!
}

class NullableWrapper<T> : INullableWrapper
    where T : struct
{
    public T? Nullable { get; private set; }

    public bool HasValue { get { return this.Nullable.HasValue; } }

    object INullableWrapper.Value { get { return this.Nullable.Value; } }

    public T Value { get { return this.Nullable.Value; } }

    public NullableWrapper(T? nullable)
    {
        this.Nullable = nullable;
    }
}

return new INullableWrapper[] { new NullableWrapper<int>(5), new NullableWrapper<string>("Hello") };