CODEWITHSUNDEEP
c#
alex_kart
alex_kart

Reputation: 1

How to convert Nullable<T>[] to T[]

I have code like this to convert nullable arrays to ordinary arrays

        object myCoolConvertion(object value)
        { 
          if (value is int?[])
              return Array.ConvertAll((int? [])value, x => x ?? default(int));
          if (value is double?[])
              return Array.ConvertAll((double?[])value, x => x ?? default(double));
          if (value is float?[])
              return Array.ConvertAll((float?[])value, x => x ?? default(float));
          return value;
        }

Is it possible to write universal code for any types like

 if (value is T?[])
     return Array.ConvertAll((T? [])value, x => x ?? default(int));

Upvotes: 0

Views: 217

Answers (3)

Jeroen van Langen
Jeroen van Langen

Reputation: 22073

I'd rather filter the null object's out. Because default structs are not useful and can not be distinguished between a real objects.

I use the IEnumerable.OfType() for this.

using System;
using System.Linq;
                    
public class Program
{
    public static T[] ConvertWithout<T>(T?[] array) where T : struct =>
         array.OfType<T>().ToArray();
    
    public struct TestStruct
    {
        public string Name {get;set;}
    }
    
    public static void Main()
    {
        var testArray = new TestStruct?[] 
        {
            new TestStruct { Name = "Peter"}, 
            null, 
            new TestStruct{Name="John"}
        };
        
        var result = ConvertWithout(testArray);
        
        foreach(var person in result)
            Console.WriteLine(person.Name);
    }
}

results:

Peter
John

Upvotes: 2

Peter Csala
Peter Csala

Reputation: 22819

Just a side note for Iridium's answer: The Nullable<T> has a method called GetValueOrDefault, which can make your code a bit more concise:

T[] Convert<T>(T?[] array) where T : struct
   => Array.ConvertAll(array, t => t.GetValueOrDefault());

Upvotes: 2

Iridium
Iridium

Reputation: 23731

You can do this with a generic method, e.g.:

T[] Convert<T>(T?[] array) where T : struct
{
    return Array.ConvertAll(array, t => t ?? default(T));
}

Upvotes: 4

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