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Saturday, December 3, 2016

Using Object Based Output as Opposed to String Based Output

Object based output is a key difference between our DOS applications and PowerShell.  Take a look at the output of PING and Test-Connection.

Pinging with 32 bytes of data:
Reply from bytes=32 time=41ms TTL=57
Reply from bytes=32 time=38ms TTL=57
Reply from bytes=32 time=40ms TTL=57
Reply from bytes=32 time=37ms TTL=57

Ping statistics for
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 37ms, Maximum = 41ms, Average = 39ms

PS C:\> Test-Connection

Source        Destination     IPV4Address      IPV6Address                              Bytes    Time(ms)
------        -----------     -----------      -----------                              -----    --------
JASONPC2                                                   32       40      
JASONPC2                                                   32       40      
JASONPC2                                                   32       46      
JASONPC2                                                   32       37  

Each has a time value.  The difference is that PING produces string where Test-Connection produces objects

PS C:\> Ping | Get-Member
    TypeName: System.String

Name             MemberType            Definition                                                                                                           
----             ----------            ----------                                                                                                          
Clone            Method                System.Object Clone(), System.Object ICloneable.Clone()                                                             
CompareTo        Method                int CompareTo(System.Object value), int CompareTo(string strB), int IComparable.CompareTo(System.Object obj), int ...
Contains         Method                bool Contains(string value)                                                                                         
CopyTo           Method                void CopyTo(int sourceIndex, char[] destination, int destinationIndex, int count)                                   
EndsWith         Method                bool EndsWith(string value), bool EndsWith(string value, System.StringComparison comparisonType), bool EndsWith(st...
Equals           Method                bool Equals(System.Object obj), bool Equals(string value), bool Equals(string value, System.StringComparison compa...
GetEnumerator    Method                System.CharEnumer

PS C:\> Test-Connection | Get-Member

   TypeName: System.Management.ManagementObject#root\cimv2\Win32_PingStatus

Name                           MemberType     Definition                                                                                                   
----                           ----------     ----------                                                                                                   
PSComputerName                 AliasProperty  PSComputerName = __SERVER                                                                                    
Address                        Property       string Address {get;set;}                                                                                     
BufferSize                     Property       uint32 BufferSize {get;set;}                                                                                 
NoFragmentation                Property       bool NoFragmentation {get;set;}                                                                              
PrimaryAddressResolutionStatus Property       uint32 PrimaryAddressResolutionStatus {get;set;}                                                              
ProtocolAddress                Property       string ProtocolAddress {get;set;}                 

Let’s try to filter for only returns that have a time that is greater than 40.

PS C:\> Ping | Where ResponceTime -gt 40

PS C:\> 

We get noting because a string object does not have a property for ResponceTime or any property for that matter.

PS C:\> Test-Connection | Where ResponseTime -gt 40

Source        Destination     IPV4Address      IPV6Address                              Bytes    Time(ms)
------        -----------     -----------      -----------                              -----    --------
JASONPC2                                                   32       42      
JASONPC2                                                   32       46   

Since Test-Connection produces an object with a property called ResponceTime, we are able to examine its value and use it. 

Here is the difference between using objects and not.  In this example, I want to see only responses from PING where the TIME value is greater than 20.  Since PING places characters on the screen, I need to capture those characters and teach PowerShell where in the string to look for the response time. Here is the code.

Ping |
    ForEach-Object {
        If ($_ -like "*=*") {
            $OrigionalString = $_
            $String = ($_.Remove(0,$_.IndexOf("=")+1))
            $String2 = $String.Remove($String.IndexOF(" "))
            $String2 -as [Int] |
                Where {$_ -gt 20} |
                ForEach-Object {Write-Output $OrigionalString}


Here is the same operation using the object produced by Test-Connection

Test-Connection | Where ResponseTime  -gt 20

Clearly using objects is going to save you a lot of time in developing, test, and supporting your code.  That fact that we have properties means that we have usable information.

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