Allow Integer Parameter to Accept Null in a PowerShell Function
One of the great things about PowerShell being based on .NET is that we get to the huge number of types built into the framework.
A problem I came across today was that I needed to have a function that took a mandatory integer parameter, but that parameter needed to allow Null. In .NET there is a generic type System.Nullable
This allows me to call the function above with the following:
Set-AdapterVlan -Adapter $adapter -Vlan $null
Which will clear the Vlan ID from the virtual network adapter.
The magic is in the parameter definition:
[Parameter(Mandatory = $true)] [AllowNull()] [Nullable[System.Int32]] $VlanId
The [AllowNull()] attribute allows the $VlanId parameter to accept a Null even though it is mandatory, and the [Nullable[System.Int32]] allows $VlanId to be assigned a null value.
This isn’t something I use often, but thought it was worth sharing.