powershell-ise

Issue with converting string "0" to $false

I can't work this out. I am storing 0's and 1's in a CSV file, in the column named "Test". Using import-csv to read them back into Powershell, in an array, and in a for loop have used:

  1. [System.Convert]::ToBoolean($Array[$i].Test) Produces error "Exception calling "ToBoolean" with "1" argument(s): "String was not recognized as a valid boolean"

  2. [boolean]($Array[$i].Test) which at least doesn't error out, but does make both 0 and 1 return as true.

Here is tests on $Array[0].Test:

Value (delimited with "'s):
"0"

GetType():

IsPublic IsSerial  Name     BaseType
-------- --------  ----     --------
True     True     String  System.Object

EDIT:

Did more tests.

Created a PSObject to be equivalent to the $String.Test:

$String = [pscustomobject]@{
    Test = 0
    }

Running gettype() against it I get:

IsPublic IsSerial    Name               BaseType                                                                                                      
-------- --------    ----               --------                                                                                                      
  True     True      Int32           System.ValueType

Then putting it into CSV:

$Array | export-csv c:\temp\test.csv -notypeinformation -noclobber -erroraction silentlycontinue

And back into an array:

$Array2 = import-csv C:\temp\test.csv

Running gettype() against $Array2[0].test:

IsPublic IsSerial    Name      BaseType                                                                                                      
-------- --------    ----      --------                                                                                                      
  True     True     String   System.Object

I notice that Base Type is now System.Object, not 'System.ValueType', though not sure if this has any bearing on the problem.

But still, why is a 0 in string form not being converted to $false?

Solution

  • On re-read of the casting rules on MS' website I see the problem. Int will convert 0 to $false, 1 to $true. But string is evaluated on it's length?! (Zero length, $false; Any other length $true). Only char (for those that need a reminder, a single character variable class) of 0/1 will convert to their int relative boolean values.