int array cannot use length property inside linq expression

Question

I have this very simple c# statement

       var list = new int[4];

        var query1 = from element in list
                     where element.Length > 10
                     select element;

and for some reason it's not letting me use Length property of int array and throwing me a following exception:

'int' does not contain a definition for 'Length' and no extension method 
'Length' accepting a first argument of type 'int' could be found (press F4 
to add a using directive or assembly reference)

i cannot figure what's going on. if i write the following:

 var query1 = from element in list.Length
                     where element > 10
                     select element;

then it works.

The query iterates through all elements of `list`. Those elements are of type `int` not of type `int[]`. — heijp06, Mar 18 '16 at 07:59
nothing. i was playing with linq expressions and converting from string array to int array i started having this issue and did not realise till i received the answers from stackoverflow. — Baahubali, Mar 18 '16 at 08:09

score 2 · Answer 1 · answered Mar 18 '16 at 08:02

from element means that linq is going to loop over all ints in list and every int is from then on called element.

See it as a foreach loop. You now wrote something like this:

foreach(int element in list)
{
    if(element.Length > 10) // an int doesn't have a Length property
    {
        yield return element;
    }
}

I am not sure what you are trying to achieve with the length property, but this is what you wrote. Could you describe what you want to assess with the length property?

score 1 · Answer 2 · answered Mar 18 '16 at 08:02

When you write from element in list you say that you want to enumerate over each element of list so element is of type int. No Length property on int type exists. Hence the error.
When you write from element in list.Length you want to enumerate over single item which is the length of the array and that item is of type int.

score 1 · Answer 3 · edited May 23 '17 at 10:28

1

element is an int retrieved from the array list. It isn't the array itself.

Since int doesn't have a Length property, it doesn't work. If you are looking for the number of digits of the integer, take a look here: How can I get a count of the total number of digits in a number?.

The end result would be:

var list = new int[4];

var query1 = from element in list
             where (element == 0 ? 1 : Math.Floor(Math.Log10(Math.Abs(element)) + 1)) > 10
             select element;

edited May 23 '17 at 10:28

Community

1
1

answered Mar 18 '16 at 08:03

Patrick Hofman

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Thank you. It makes perfect sense. – Baahubali Mar 18 '16 at 08:06
1

`Math.Log10(element)` will fail on *zero* and *negative items*; `var list = new int[] {0, -1, -2, -3};` – Dmitry Bychenko Mar 18 '16 at 08:09
A subtle error: `Math.Abs(element)` can fail on `element == int.MinValue` (integer overflow error) – Dmitry Bychenko Mar 18 '16 at 08:14

score 1 · Accepted Answer · answered Mar 18 '16 at 08:03

The issue is with your query:

   var list = new int[4];

    var query1 = from element in list
                 where element.Length > 10
                 select element;

Here the element is an individual integer from the array listand not a int[]. So obviously Length doesn't exist for int type.

Dmitry Bychenko · Answer 5 · 2016-03-18T08:26:24.187

The compiler is right: int doesn't have any Length property (and list is an array of ints). Do you mean string representation of int?

var list = new int[4];
...

var query = list
  .Where(element => element.ToString().Length > 10) // note "ToString()"
  .Select(element);

Please note, that the query, probably, will return an empty enumerable: the longest string representation of int in most cultures is -2147483648 which has exactly 10 digits. If you want count digits (e.g. -123 has three digits) you can modify the query a little:

var query = list
  .Where(element => element
    .ToString(CultureInfo.InvariantCulture)
    .Trim('-')
    .Length > 10) 
  .Select(element);

And in this case, you will definitely have an empty result.

score 0 · Answer 6 · answered Mar 18 '16 at 08:17

Your code is similar to this:

var list = new int[4];            
var filteredElements = new List<int>();
foreach (int element in list)
{
  if(element.Length > 10)
  {
    filteredElements.Add(element);
  }
}

That's why you get error 'int' does not contain a definition for 'Length' and no extension method

int array cannot use length property inside linq expression

6 Answers6