TryParsing from an object list to int | c#

Question

I'm trying to take objects out of an object list to an int list. If the object list's value contains a string than I want to convert it to an int. the error that I'm getting is "cannot convert from 'object' to 'System.ReadOnlySpan'. I've tried looking up examples and information about lists made of objects but couldn't find anything.

I'm also at a loss as to what to do with the 'else' part of the code.

public class ListFilterer
{
   public static IEnumerable(int) GetIntegersFromList(List(object) listOfItems)
   {

      List<int> Integers = new List<int>();

      foreach (var value in listOfItems)
      {
        int number = 0;

        bool success = Int32.TryParse(value, out number);

        if (success)
        {
          Integers.Add(number);
        }
        else
        {
          Integers.Add(number);
        }
      }
      return Integers;

   }
}

don't use parse it will give you error, get type of object if its int then parse it otherwise ignore it — Ari
– Ari, Commented Mar 5, 2020 at 6:36

Caius Jard · Accepted Answer · 2020-03-05 07:03:46Z

1

It'll probably work out if you TryParse value.ToString() instead, if you're looking for anything that might look like an int and can be converted to an int. If you only want things that actually are ints, something like if(value is int number) should work if your c# version is recent. If it's older you may have to if(value is int) and then cast the value inside the if

Your code can be simplified to:

foreach(...){

  int.TryParse(value.ToString(), out var n);
  integers.Add(n);

}

Or

foreach(...){

  if(value is int)
    integers.Add((int)value);
  else 
    integers.Add(0);
}

edited Mar 5, 2020 at 7:03

answered Mar 5, 2020 at 6:37

Caius Jard

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1 Comment

Caius Jard Over a year ago

No probs. I added a bit more advice too

Michał Turczyn · Accepted Answer · 2020-03-05 06:51:20Z

1

You could simply use:

var ints = listOfItems
  .Select(o => { int.TryParse(o.ToString(), out int num); return num;} )
  .ToList();

This will work as you wish, as if conversion fails num is 0 by default.

answered Mar 5, 2020 at 6:51

Michał Turczyn

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Comments

Alexander · Accepted Answer · 2020-03-05 06:39:51Z

0

If Try Parse fails number is automatically 0 so you can directly write this

 Int32.TryParse(value, out int number)
 Integers.Add(number);

answered Mar 5, 2020 at 6:39

Alexander

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2 Comments

Excanator Over a year ago

yep! thank you this and the comment above in combination made the code work! thank you!

ProgrammingLlama Over a year ago

value is object, not string.

Alexander · Accepted Answer · 2020-03-05 06:57:12Z

0

Maybe you can find the better way

var intList = objs.ConvertAll(delegate (object obj) { return (int)obj; });

answered Mar 5, 2020 at 6:57

Alexander

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1 Comment

Alexander Over a year ago

where objs is the list of objects

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