咆哮:我什至非常非常生气,我们可以实例化 System.Management.Automation.ParameterMetadata 类型,但我们无法初始化它。微软通过使用私有或内部或密封的类来限制类,破坏了类库的许多乐趣......他们经常使用它,而且没有任何可以想到的理由。这是一个非常疯狂的图书馆设计!吐槽:
对于元编程和创建 ProxyCommands(代理函数),我需要从头开始以编程方式创建 Windows PowerShell 参数。我什至不喜欢闯入课堂偷窃和使用 vorbidden 的东西,这可能会发生变化。即使是序列化技巧也是在不同的路线上做同样的肮脏方式。
这是我的解决方案原型。我正在创建一个带有参数作为文本的函数(函数源代码)。我的第一次尝试是在函数驱动器中执行一个 New-Item Function:\ -value {code},然后对新函数执行一个 Get-Command 以提取元数据。但这表明,该函数是一匹死去的 sorcecode 只有马。它没有被编译。所以我不得不使用 Invoke-Expression 来“编译”函数的源代码。
Function New-Parameter {
[CmdletBinding()]
param(
[Switch]$Mandatory,
[UInt32]$Position,
[Switch]$ValueFromPipeline,
[Switch]$ValueFromPipelineByPropertyName,
[Switch]$ValueFromRemainingArguments,
[String]$HelpMessage,
[Type]$Type=[Type]'System.Management.Automation.SwitchParameter',
[Parameter(Mandatory=$True)]
[String]$Name,
[String]$DefaultValue,
[Switch]$DontShow,
[String[]]$ParameterSetName,
[String[]]$Aliases,
# if Metadata is present the result is an System.Management.Automation.ParameterMetadata object
# If Metadata is absent the sourcecode for the Parameter is returned
[Switch]$Metadata
)
$ParameterAttrib = [System.Collections.ArrayList]@()
# using GUID to create an unique function Name
$Guid = ([Guid]::NewGuid()).ToString()
# using a StringBuilder to glue the sourcecode
$stringBuilder = New-Object System.Text.StringBuilder
If($Metadata.IsPresent) {
# Open the Function{} block
[Void]$stringBuilder.AppendLine("Function $Guid {")
# add the [CmdletBinding()] attribute
[Void]$stringBuilder.AppendLine("[CmdletBinding()]")
# Open the Param() block
[Void]$stringBuilder.AppendLine("param(")
}
# query if we have one or more ParameterSetName
$ParmameterSetNameCount = 0
If(-not [String]::IsNullOrEmpty($ParameterSetName)) {
$ParmameterSetNameCount = @($ParameterSetName).Count
}
# Open the [Parameter()] attribut
[Void]$stringBuilder.Append('[Parameter(')
If($Mandatory.IsPresent) {
[Void]$ParameterAttrib.Add('Mandatory=$True')
}
If($Position) {
[Void]$ParameterAttrib.Add("Position=$Position")
}
If($ParmameterSetNameCount -gt 0){
# in the first full blown [Parameter()] attribut allways insert the first ParametersetName
[Void]$ParameterAttrib.Add("ParameterSetName='$($ParameterSetName[0])'")
}
If($ValueFromPipeline.IsPresent) {
[Void]$ParameterAttrib.Add('ValueFromPipeline=$True')
}
If($ValueFromPipelineByPropertyName.IsPresent) {
[Void]$ParameterAttrib.Add('ValueFromPipelineByPropertyName=$True')
}
If($ValueFromRemainingArguments.IsPresent) {
[Void]$ParameterAttrib.Add('ValueFromRemainingArguments=$True')
}
If($DontShow.IsPresent) {
If($PSVersionTable.PSVersion.Major -lt 4) {
Write-Warning "The 'DontShow' attribute requires PowerShell 4.0 or above! `n Supressing the 'DontShow' attribute!"
} Else {
[Void]$ParameterAttrib.Add('DontShow')
}
}
If(-not [String]::IsNullOrEmpty($HelpMessage)) {
[Void]$ParameterAttrib.Add("HelpMessage='$HelpMessage'")
}
# generate comma separated list from array
[Void]$stringBuilder.Append("$($ParameterAttrib -Join ',')")
$ParameterAttrib.Clear()
# close the [Parameter()] attribut
[Void]$stringBuilder.AppendLine(")]")
$ParmameterSetLoopCounter++
# If we have more then one ParametersetName
IF($ParmameterSetNameCount -gt 1) {
# add remaining parameterset names the parameter belongs to
for ($i = 1; $i -lt $ParmameterSetNameCount; $i++) {
[Void]$stringBuilder.AppendLine("[Parameter(ParameterSetName='$($ParameterSetName[$i])')]")
}
}
# Create Alias Attribute from Aliases
If(-not [String]::IsNullOrEmpty($Aliases)) {
[Void]$stringBuilder.AppendLine("[Alias('$($Aliases -join "','")')]")
}
# add Parameter Type
[Void]$stringBuilder.Append("[$($Type.Fullname)]")
# add the Parameter Name
[Void]$stringBuilder.Append("`$$Name")
If(-not [String]::IsNullOrEmpty($ParameterSetName)) {
[Void]$stringBuilder.Append("=$DefaultValue")
}
If($Metadata.IsPresent) {
# close the Param() block
[Void]$stringBuilder.AppendLine()
[Void]$stringBuilder.AppendLine(')')
# close the Function block
[Void]$stringBuilder.AppendLine('}')
}
# return the result
If($Metadata.IsPresent) {
# if we have to return a ParameterMetadata Object we create a temporary function
# because you can instatiate a ParameterMetadata Object but most of the Properties are constrained to get only and not to set!
# Create and 'compile' the function into the function: drive
Invoke-Expression ($stringBuilder.ToString())
# from the temporary function we query the the ParameterMetadata and
# return theParameterMetadata Object
(Get-Command -Name $Guid -CommandType Function).Parameters.$Name
# remove the Function from Function: drive
$Null = Remove-Item Function:\$Guid -Force
} Else {
# return the sourcecode of the Parameter
Write-Output $stringBuilder.ToString()
}
}
#Example calls:
# without Parametersets
New-Parameter -Name 'Param1' -Mandatory -Position 3 -ValueFromPipeline -ValueFromPipelineByPropertyName -ValueFromRemainingArguments -HelpMessage "Give me hope Joana!" -Type 'System.String' -Aliases 'Ali1','Ali2','Ali3' -DontShow -DefaultValue 34
New-Parameter -Name 'Param1' -Mandatory -Position 3 -ValueFromPipeline -ValueFromPipelineByPropertyName -ValueFromRemainingArguments -HelpMessage "Give me hope Joana!" -Type 'System.String' -Aliases 'Ali1','Ali2','Ali3' -DontShow -DefaultValue 34 -Metadata
# with Parametersets
New-Parameter -Name 'Param1' -Mandatory -Position 3 -ValueFromPipeline -ValueFromPipelineByPropertyName -ValueFromRemainingArguments -HelpMessage "Give me hope Joana!" -Type 'System.String' -ParameterSetName 'Snover','Payette' -Aliases 'Ali1','Ali2','Ali3' -DontShow -DefaultValue 34
New-Parameter -Name 'Param1' -Mandatory -Position 3 -ValueFromPipeline -ValueFromPipelineByPropertyName -ValueFromRemainingArguments -HelpMessage "Give me hope Joana!" -Type 'System.String' -ParameterSetName 'Snover','Payette' -Aliases 'Ali1','Ali2','Ali3' -DontShow -DefaultValue 34 -Metadata
我是否正确构建参数集?