How can you test if an object has a specific property? - powershell

Question

How can you test if an object has a specific property?
Appreciate I can do ...
$members = Get-Member -InputObject $myobject
and then foreach through the $members, but is there a function to test if the object has a specific property?
Additional Info:
The issue is I'm importing two different sorts of CSV file, one with two columns, the other with three. I couldn't get the check to work with "Property", only with "NoteProperty" ... whatever the difference is
if ( ($member.MemberType -eq "NoteProperty" ) -and ($member.Name -eq $propertyName) )

Answer 1

Like this?
[bool]($myObject.PSobject.Properties.name -match "myPropertyNameToTest")

Answer 2

You can use Get-Member
if (Get-Member -inputobject $var -name "Property" -Membertype Properties) {
#Property exists
}

Answer 3

This is succinct and readable:
"MyProperty" -in $MyObject.PSobject.Properties.Name
We can put it in a function:
function HasProperty($object, $propertyName)
{
$propertyName -in $object.PSobject.Properties.Name
}

Answer 4

For me MyProperty" -in $MyObject.PSobject.Properties.Name didn't work, however
$MyObject.PSobject.Properties.Name.Contains("MyProperty")
works

Answer 5

There are a number of solutions to this question that work in strict mode, but some are better than others.
Solutions that do not appear to iterate through every property are the fastest solutions.
Bernie White's solution and
esskar's solution (modified)
Solutions that look as though they iterate through every property are slower.
sebke CCU's solution and
dan-gph's solution
The solution that appears to iterate through every property and uses a regular expression is a little slower than the previous two solutions (because compiling and executing the regular expression takes more time)
CB.'s solution
The solution that uses GetMethod appears to iterate through every property, but its use of GetMethod makes it significantly slower.
Paul's GetMethod solution
The following script was used to compare the previously mentioned solutions in strict mode:
# Tested in PowerShell core 7.2.0
Set-StrictMode -Version Latest
$propertyExistsMethods = New-Object System.Collections.Generic.Dictionary'[string,scriptblock]'
# Fastest
$propertyExistsMethods.Add(
"PSObject.Properties (Bernie White's solution)",
{
Param( [PSObject] $Object, [string] $Property )
[bool]$Object.PSObject.Properties[$Property]
})
$propertyExistsMethods.Add(
"PSObject.Properties.Item (esskar's solution (modified))",
{
Param( [PSObject] $Object, [string] $Property )
[bool]$Object.PSObject.Properties.Item($property)
})
# Not as fast
$propertyExistsMethods.Add(
"Contains (sebke CCU's solution)",
{
Param( [PSObject] $Object, [string] $Property )
$Object.PSobject.Properties.Name.Contains($Property)
})
$propertyExistsMethods.Add(
"-in (dan-gph's solution)",
{
Param( [PSObject] $Object, [string] $Property )
$Property -in $Object.PSobject.Properties.Name
})
# Slower than the previously mentioned solutions
$propertyExistsMethods.Add(
"-match (CB.'s solution)",
{
Param( [PSObject] $Object, [string] $Property )
[bool]($Object.PSobject.Properties.name -match $Property)
})
# Slowest
$propertyExistsMethods.Add(
"GetMember (Paul's solution)",
{
Param( [PSObject] $Object, [string] $Property )
Get-Member -inputobject $Object -name $Property -Membertype Properties
})
foreach ($method in $propertyExistsMethods.Keys) {
$propertyExists = $propertyExistsMethods[$method]
$o = #{}
foreach ($i in 1..100000) {
$o[$i] = "p$i"
}
Write-Host $method
$measure = Measure-Command {
foreach ($i in 1..100000) {
# Always check for a property that does NOT exist
& $propertyExists -Object $o -Property 'p'
}
}
Write-Host $measure | % { $_.Milliseconds }
Write-Host ''
}
The output is as follows:
PSObject.Properties (Bernie White's solution)
00:00:03.1437587
PSObject.Properties.Item (esskar's solution)
00:00:03.5833642
Contains (sebke CCU's solution)
00:00:04.4812702
-in (dan-gph's solution)
00:00:04.6507811
-match (CB.'s solution)
00:00:05.1107066
GetMember (Paul's solution)
00:00:14.5305115

Answer 6

Try this for a one liner that is strict safe.
[bool]$myobject.PSObject.Properties[$propertyName]
For example:
Set-StrictMode -Version latest;
$propertyName = 'Property1';
$myobject = [PSCustomObject]#{ Property0 = 'Value0' };
if ([bool]$myobject.PSObject.Properties[$propertyName]) {
$value = $myobject.$propertyName;
}

Answer 7

I've been using the following which returns the property value, as it would be accessed via $thing.$prop, if the "property" would be to exist and not throw a random exception. If the property "doesn't exist" (or has a null value) then $null is returned: this approach functions in/is useful for strict mode, because, well, Gonna Catch 'em All.
I find this approach useful because it allows PS Custom Objects, normal .NET objects, PS HashTables, and .NET collections like Dictionary to be treated as "duck-typed equivalent", which I find is a fairly good fit for PowerShell.
Of course, this does not meet the strict definition of "has a property".. which this question may be explicitly limited to. If accepting the larger definition of "property" assumed here, the method can be trivially modified to return a boolean.
Function Get-PropOrNull {
param($thing, [string]$prop)
Try {
$thing.$prop
} Catch {
}
}
Examples:
Get-PropOrNull (Get-Date) "Date" # => Monday, February 05, 2018 12:00:00 AM
Get-PropOrNull (Get-Date) "flub" # => $null
Get-PropOrNull (#{x="HashTable"}) "x" # => "HashTable"
Get-PropOrNull ([PSCustomObject]#{x="Custom"}) "x" # => "Custom"
$oldDict = New-Object "System.Collections.HashTable"
$oldDict["x"] = "OldDict"
Get-PropOrNull $d "x" # => "OldDict"
And, this behavior might not [always] be desired.. ie. it's not possible to distinguish between x.Count and x["Count"].

Answer 8

Just check against null.
($myObject.MyProperty -ne $null)
If you have not set PowerShell to StrictMode, this works even if the property does not exist:
$obj = New-Object PSObject;
Add-Member -InputObject $obj -MemberType NoteProperty -Name Foo -Value "Bar";
$obj.Foo; # Bar
($obj.MyProperty -ne $null); # False, no exception

Answer 9

If you are using StrictMode and the psobject might be empty, it will give you an error.
For all purposes this will do:
if (($json.PSobject.Properties | Foreach {$_.Name}) -contains $variable)

Answer 10

I find this method more strict and faster when checking multiple properties
$null -ne $myobject.PSObject.Properties.Item("myPropertyNameToTest")

Answer 11

Real similar to a javascript check:
foreach($member in $members)
{
if($member.PropertyName)
{
Write $member.PropertyName
}
else
{
Write "Nope!"
}
}

Answer 12

Just to clarify
given the following object
$Object
With the following properties
type : message
user : john.doe#company.com
text :
ts : 11/21/2016 8:59:30 PM
The following are true
$Object.text -eq $NULL
$Object.NotPresent -eq $NULL
-not $Object.text
-not $Object.NotPresent
So the earlier answers that explicitly check for the property by name is the most correct way to verify that that property is not present.

Answer 13

I ended up with the following function ...
function HasNoteProperty(
[object]$testObject,
[string]$propertyName
)
{
$members = Get-Member -InputObject $testObject
if ($members -ne $null -and $members.count -gt 0)
{
foreach($member in $members)
{
if ( ($member.MemberType -eq "NoteProperty" ) -and `
($member.Name -eq $propertyName) )
{
return $true
}
}
return $false
}
else
{
return $false;
}
}

Answer 14

I recently switch to set strict-mode -version 2.0 and my null tests failed.
I added a function:
#use in strict mode to validate property exists before using
function exists {
param($obj,$prop)
try {
if ($null -ne $obj[$prop]) {return $true}
return $false
} catch {
return $false
}
return $false
}
Now I code
if (exists $run main) { ...
rather than
if ($run.main -ne $null) { ...
and we are on our way. Seems to work on objects and hashtables
As an unintended benefit it is less typing.

Answer 15

for me this work
Set-StrictMode -Version Latest
$TMP = ...
$HAS_SERVERS=($TMP | Select-Object Servers)
if (-not $HAS_SERVERS.Servers){
echo "No servers. Abort."
} else {
...
}

Answer 16

I just started using PowerShell with PowerShell Core 6.0 (beta) and following simply works:
if ($members.NoteProperty) {
# NoteProperty exist
}
or
if (-not $members.NoteProperty) {
# NoteProperty does not exist
}

Answer 17

You could check with:
($Member.PropertyNames -contains "Name") this will check for the Named property

Answer 18

For identifying which of the objects in an array have a property
$HasProperty = $ArrayOfObjects | Where-Object {$_.MyProperty}