Powershell hashtable with multiple values and one key - powershell

Question

Im looking for a data structure/cmdlet that will allow me to add multiple values to a single key in Powershell.
My data would ideally look like this:
KEY-------------------------- VALUES
HOSTNAME1-------------DATABASE1,DATABASE2,DATABASE3
HOSTNAME2-------------DATABASE1,DATABASE2
etc...
I thought a hashtable would do the trick, but I'm unable to do the following:
$servObjects = #{}
$servObjects.Add("server1", #())
$servObjects.get_item("server1") += "database1"
This yields an empty array when I try:
$servObjects.get_item("server1")
I have also tried to do the following, hoping that powershell would understand what I want:
$servObjects2 = #{}
$servObjects2.add($servername, $databasename)
This will unfortunately yield a duplicate key exception
Thanks for any and all input

Answer 1

You basically want a hash table with values that are arrays. You don't have to use $hashtable.get_item or .add
$myHashTable = #{} # creates hash table
$myHashTable.Entry1 = #() #adds an array
$myHashTable.Entry1 += "element1"
$myHashTable.Entry1 += "element2"
This results in the following output:
$myHashTable
Name Value
---- -----
Entry1 {element1, element2}
$myHashTable.Entry1
element1
element2

Answer 2

If you have your data in an array you can group the array and convert to a hash table:
$ary = #()
$ary = $ary + [PSCustomObject]#{RowNumber = 1; EmployeeId = 1; Value = 1 }
$ary = $ary + [PSCustomObject]#{RowNumber = 2; EmployeeId = 1; Value = 2 }
$ary = $ary + [PSCustomObject]#{RowNumber = 3; EmployeeId = 2; Value = 3 }
$ary = $ary + [PSCustomObject]#{RowNumber = 4; EmployeeId = 2; Value = 4 }
$ary = $ary + [PSCustomObject]#{RowNumber = 5; EmployeeId = 3; Value = 5 }
$ht = $ary | Group-Object -Property EmployeeId -AsHashTable
$ht is then:
Name Value
---- -----
3 {#{RowNumber=5; EmployeeId=3; Value=5}}
2 {#{RowNumber=3; EmployeeId=2; Value=3}, #{RowNumber=4; EmployeeId=2; Value=4}}
1 {#{RowNumber=1; EmployeeId=1; Value=1}, #{RowNumber=2; EmployeeId=1; Value=2}}

Answer 3

In your original example, instead of writing
$servObjects.get_item("server1") += "database1"
you had written
$servObjects.server1 += "database1"
it would have worked.
I'm very new to PowerShell, but I prefer to use
$servObjects.Add("key",#())
over
$servObjects.key = #())
because the .Add will throw a duplicate exception if the key is already present in the hashtable, whereas the assignment will replace an existing entry with a new one. For my purposes, I have found that the implicit replacement is (more often than not) an error, either in my logic, or an anomaly in the input data that needs to be handled.

Answer 4

If you know the value at creation time, it would be clearer this way :
[hashtable]$hash = #{
HOSTNAME1 = #(DATABASE1, DATABASE2, DATABASE3);
HOSTNAME2 = #(DATABASE1, DATABASE2);
}
Which will get you the following :
Name Value
---- -----
HOSTNAME2 {DATABASE1, DATABASE2}
HOSTNAME1 {DATABASE1, DATABASE2, DATABASE3}