一些 PowerShell commandlet 接受管道输入 ByProperyName，一些接受 ByValue，另一些则同时接受两者。这是什么意思？它如何影响我们的 PowerShell 脚本？
The ValueFromPipeline参数属性 http://msdn.microsoft.com/en-us/library/system.management.automation.parameterattribute.valuefrompipeline%28v=vs.85%29.aspx会将参数值映射到从管道传入的任何对象类型。如果您使用ValueFromPipelineByPropertyName参数属性 http://msdn.microsoft.com/en-us/library/system.management.automation.parameterattribute.valuefrompipelinebypropertyname%28v=vs.85%29.aspx，那么将从通过管道传输到命令+参数的对象中使用特定属性。
ValueFromPipeline 示例
Get-Process | Stop-Process; # Stop-Process expects to receive a Process object
<#
-InputObject <Process[]>
Stops the processes represented by the specified process objects. Enter a variable that contains the objects, or
type a command or expression that gets the objects.
Required? true
Position? 1
Default value
Accept pipeline input? true (ByValue)
Accept wildcard characters? false
#>
ValueFromPipelineByPropertyName 示例
# Get-Process looks for a ComputerName property on the incoming objects
[PSCustomObject]@{
ComputerName = 'localhost';
} | Get-Process;
<#
-ComputerName <String[]>
Gets the processes running on the specified computers. The default is the local computer.
Type the NetBIOS name, an IP address, or a fully qualified domain name of one or more computers. To specify the
local computer, type the computer name, a dot (.), or "localhost".
This parameter does not rely on Windows PowerShell remoting. You can use the ComputerName parameter of Get-Process
even if your computer is not configured to run remote commands.
Required? false
Position? named
Default value Local computer
Accept pipeline input? True (ByPropertyName)
Accept wildcard characters? false
#>
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