Vista - unexpected conversion for [System.DateTime]

Guys,
I run some asynchronous scripts and need to measure their timing:
I run into following “unexpected� conversion, below is a small script to
demonstrate it.

The question is:
Why [System.DateTime]::Now gets converted to [String] type when passed as
parameter, while a variable of [System.DateTime] type is not?
Doesn’t is look like an inconsistent behavior?

#------------------------------------------------------------------------------
function test([DateTime] $a) {

Start-Sleep -milli 200
[DateTime] $private:b = [System.DateTime]::Now
Start-Sleep -milli 200


@"
A started $a. A elapsed time $($b - $a)<br>
B started $b. B elapsed time $([System.DateTime]::Now - $b)<br>
Total elapsed time $([System.DateTime]::Now - $a)<br>
"@

}


#------------------------------------------------------------------------------
function test2($a) {
$a.GetType()
}


#------------------------------------------------------------------------------
#-- Main script
---------------------------------------------------------------
#------------------------------------------------------------------------------


# Works fine
[DateTime] $private:x = [System.DateTime]::Now
test $x
test2 $x


# Doesn't work
test [System.DateTime]::Now
test2 [System.DateTime]::Now

return

#------------------------------------------------------------------------------
#------------------------------------------------------------------------------
#------------------------------------------------------------------------------

> ./g
A started 10/29/2006 13:24:24. A elapsed time 00:00:00.2031224<br>
B started 10/29/2006 13:24:24. B elapsed time 00:00:00.2031224<br>
Total elapsed time 00:00:00.4062448<br>

IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True DateTime System.ValueType
test : Cannot convert value "[System.DateTime]::Now" to type
"System.DateTime". Error: "String was not recognized as a valid DateTime."
At .\g.ps1:37 char:5
+ test <<<< [System.DateTime]::Now
True True String System.Object

There is no unexpected conversion, because there is no conversion! :-)
The whole parameter "[System.DateTime]::Now" is simply _interpreted_ as a
string.
Then, converting the _String_ "[System.DateTime]::Now" into a DateTime will
of course fail.

function testf ($p) {$p; $p.GetType()}

PS> testf [System.DateTime]::Now
[System.DateTime]::Now

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

As you can see, the parameter gets is of type String. Therefore you should
to put your parameter inside $( ). This will calculate the value before
passing it as a parameter:

PS> test $([System.DateTime]::Now)
A started 10/29/2006 20:22:59. A elapsed time 00:00:00.2031250<br>
B started 10/29/2006 20:23:00. B elapsed time 00:00:00.2031250<br>
Total elapsed time 00:00:00.4062500<br>
PS> test2 $([System.DateTime]::Now)

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

--
greetings
dreeschkind

"OK" wrote:

> Guys,
> I run some asynchronous scripts and need to measure their timing:
> I run into following “unexpected� conversion, below is a small script to
> demonstrate it.
>
> The question is:
> Why [System.DateTime]::Now gets converted to [String] type when passed as
> parameter, while a variable of [System.DateTime] type is not?
> Doesn’t is look like an inconsistent behavior?
>
> #------------------------------------------------------------------------------
> function test([DateTime] $a) {
>
> Start-Sleep -milli 200
> [DateTime] $private:b = [System.DateTime]::Now
> Start-Sleep -milli 200
>
>
> @"
> A started $a. A elapsed time $($b - $a)<br>
> B started $b. B elapsed time $([System.DateTime]::Now - $b)<br>
> Total elapsed time $([System.DateTime]::Now - $a)<br>
> "@
>
> }
>
>
> #------------------------------------------------------------------------------
> function test2($a) {
> $a.GetType()
> }
>
>
> #------------------------------------------------------------------------------
> #-- Main script
> ---------------------------------------------------------------
> #------------------------------------------------------------------------------
>
>
> # Works fine
> [DateTime] $private:x = [System.DateTime]::Now
> test $x
> test2 $x
>
>
> # Doesn't work
> test [System.DateTime]::Now
> test2 [System.DateTime]::Now
>
> return
>
> #------------------------------------------------------------------------------
> #------------------------------------------------------------------------------
> #------------------------------------------------------------------------------
>
> > ./g
> A started 10/29/2006 13:24:24. A elapsed time 00:00:00.2031224<br>
> B started 10/29/2006 13:24:24. B elapsed time 00:00:00.2031224<br>
> Total elapsed time 00:00:00.4062448<br>
>
> IsPublic IsSerial Name BaseType
> -------- -------- ---- --------
> True True DateTime System.ValueType
> test : Cannot convert value "[System.DateTime]::Now" to type
> "System.DateTime". Error: "String was not recognized as a valid DateTime."
> At .\g.ps1:37 char:5
> + test <<<< [System.DateTime]::Now
> True True String System.Object
>
>

Right! :-)
Stupid me!
Any ideas about time truncation in the next post?
OK

"OK" wrote:

> Any ideas about time truncation in the next post?

No, sorry, I could not reproduce your results at all.
You should probably check your posted scripts again.

--
greetings
dreeschkind