This problem did interest me, so I did some real digging and I have found a solution (though I have only tested on some simple cases)!
Concept
The key solution is using [System.Type]::InvokeMember
which allows you to pass parameter names in one of its overloads.
Here is the basic concept.
$Object.GetType().InvokeMember($Method, [System.Reflection.BindingFlags]::InvokeMethod,
$null, ## Binder
$Object, ## Target
([Object[]]$Args), ## Args
$null, ## Modifiers
$null, ## Culture
([String[]]$NamedParameters) ## NamedParameters
)
Solution
Here is a reusable solution for calling methods with named parameters. This should work on any object, not just COM objects. I made a hashtable as one of the parameters so that specifying the named parameters will be more natural and hopefully less error prone. You can also call a method without parameter names if you want by using the -Argument parameter
Function Invoke-NamedParameter {
[CmdletBinding(DefaultParameterSetName = "Named")]
param(
[Parameter(ParameterSetName = "Named", Position = 0, Mandatory = $true)]
[Parameter(ParameterSetName = "Positional", Position = 0, Mandatory = $true)]
[ValidateNotNull()]
[System.Object]$Object
,
[Parameter(ParameterSetName = "Named", Position = 1, Mandatory = $true)]
[Parameter(ParameterSetName = "Positional", Position = 1, Mandatory = $true)]
[ValidateNotNullOrEmpty()]
[String]$Method
,
[Parameter(ParameterSetName = "Named", Position = 2, Mandatory = $true)]
[ValidateNotNull()]
[Hashtable]$Parameter
,
[Parameter(ParameterSetName = "Positional")]
[Object[]]$Argument
)
end { ## Just being explicit that this does not support pipelines
if ($PSCmdlet.ParameterSetName -eq "Named") {
## Invoke method with parameter names
## Note: It is ok to use a hashtable here because the keys (parameter names) and values (args)
## will be output in the same order. We don't need to worry about the order so long as
## all parameters have names
$Object.GetType().InvokeMember($Method, [System.Reflection.BindingFlags]::InvokeMethod,
$null, ## Binder
$Object, ## Target
([Object[]]($Parameter.Values)), ## Args
$null, ## Modifiers
$null, ## Culture
([String[]]($Parameter.Keys)) ## NamedParameters
)
} else {
## Invoke method without parameter names
$Object.GetType().InvokeMember($Method, [System.Reflection.BindingFlags]::InvokeMethod,
$null, ## Binder
$Object, ## Target
$Argument, ## Args
$null, ## Modifiers
$null, ## Culture
$null ## NamedParameters
)
}
}
}
Examples
Calling a method with named parameters.
$shell = New-Object -ComObject Shell.Application
Invoke-NamedParameter $Shell "Explore" @{"vDir"="$pwd"}
## the syntax for more than one would be @{"First"="foo";"Second"="bar"}
Calling a method that takes no parameters (you can also use -Argument with $null).
$shell = New-Object -ComObject Shell.Application
Invoke-NamedParameter $Shell "MinimizeAll" @{}