powershell Get-Member (MemberDefinition) to .Net MemberInfo

Question

How to transition from PowerShell reflection to .Net reflection?

If I have MemberDefinition for a Method (i.e. '' | gm -Name Insert), how can get it attributes?

Answer 1

MemberDefinition is just a POCO with 4 data members, so nothing fancy can be done here: just use those string properties to resolve type/member.

filter Resolve-NetType {
    [OutputType([System.Reflection.MemberInfo])] param()
    ([type]$_.TypeName).GetMember($_.Name)
}

'' | gm -Name ToString |
    Resolve-NetType |
    % { "$($_.GetType().Name) $($_.Name)($($_.GetParameters() | % { $_.CustomAttributes + $_.ParameterType + $_.Name}))" }

# RuntimeMethodInfo ToString()
# RuntimeMethodInfo ToString([System.Runtime.CompilerServices.NullableAttribute((Byte)2)] System.IFormatProvider provider)

@mklement0 suggested to use PSMethod (late bound delegate in terms of C#), but it's actually more tricky to do anything with it beside Invoke, since there is no direct access to original type, but we can workaround it via reflection.

$bindingFlagsAll=[System.Reflection.bindingflags]'IgnoreCase,Instance,Static,NonPublic,Public'

function Get-Target {
    [OutputType([object])] param([System.Management.Automation.PSMemberInfo]$PSMember)
    [System.Management.Automation.PSMemberInfo].GetField('instance', $bindingFlagsAll).GetValue($PSMember)
}

So combined:

filter Resolve-NetType {
    [OutputType([System.Reflection.MemberInfo])] param()
    # TODO: check $_.MemberType to filter out ETS members
    if ($_ -is [Microsoft.PowerShell.Commands.MemberDefinition])
    { ([type]$_.TypeName).GetMember($_.Name) }
    else
    { (Get-Target $_).GetType().GetMember($_.Name) }
}

(''.Chars, ($true | gm -Name ToString)) |
    Resolve-NetType |
    % { "$($_.GetType().Name) $($_.CustomAttributes) $($_.Name)" }

# RuntimePropertyInfo  Chars
# RuntimeMethodInfo [System.Runtime.CompilerServices.NullableContextAttribute((Byte)1)] ToString
# RuntimeMethodInfo [System.Runtime.CompilerServices.NullableContextAttribute((Byte)1)] ToString