PowerShell for Microsoft SharePoint 2010 : Variables, Arrays, and Hashtables - Hashtables in Windows PowerShell

Windows PowerShell also includes hashtables, or associative arrays. Hashtables use key/value pairs instead of a numeric index to access the elements.

You can create a hashtable by placing one or more key/value pairs inside @{}.

PS > $hashTable = @{"FirstName"="Jean-Luc";"LastName"="Picard"}
PS > $hashTable

Name                           Value
----                           -----
FirstName                      Jean-Luc
LastName                       Picard

You can access specific elements in a hashtable in two ways: using dot notation or by typing the key within square brackets. Here’s how to use dot notation:

PS > $hashTable.FirstName
Jean-Luc
PS > $hashTable.LastName
Picard

And here’s the square bracket form:

PS > $hashTable["FirstName"]
Jean-Luc
PS > $hashTable["LastName"]
Picard

You can also send a hashtable down a pipeline and use the Select-Object cmdlet to retrieve specific elements.

PS > $hashTable | Select @{Name="Name";Expression={$_["FirstName"]}}

Name
----
Jean-Luc

To change a key/value pair in a hashtable, you can use either form to access it and assign the new value, as in these examples:

PS > $hashTable.FirstName = "William"
PS > $hashTable["LastName"] = "Riker"
PS > $hashTable

Name                           Value
----                           -----
LastName                       Riker
FirstName                      William

You can also store multiple hashtables in an array. In this example, we store two hashtables in an array.

PS > $hashTable = @{"FirstName"="Jean-Luc";"LastName"="Picard"},
@{"FirstName"="William";"LastName"="Riker"}
PS > $hashTable

Name                           Value
----                           -----
LastName                       Picard
FirstName                      Jean-Luc
LastName                       Riker
FirstName                      William

When multiple hashtables are in an array, to access elements in the hashtable, you need to index into a specific element; otherwise, Windows PowerShell will not know which element you want to retrieve.

PS > $hashTable[0]
PS > $hashTable[0].FirstName

Name                           Value
----                           -----
LastName                       Picard
FirstName                      Jean-Luc

In this example, we retrieve the first hashtable in the array and return the key/value pair.