如何在Powershell中调用自定义类的通用静态方法？
给定以下类：
public class Sample
{
public static string MyMethod<T>( string anArgument )
{
return string.Format( "Generic type is {0} with argument {1}", typeof(T), anArgument );
}
}
这将被编译成一个程序集 'Classes.dll' 并像这样加载到 PowerShell 中:
Add-Type -Path "Classes.dll"
如@Athari所说，调用MyMethod最简单的方法是使用MakeGenericMethod。虽然他实际上没有展示如何实现，但这里有一个经过验证的可工作代码示例：
$obj = New-Object Sample
$obj.GetType().GetMethod("MyMethod").MakeGenericMethod([String]).Invoke($obj, "Test Message")
$obj.GetType().GetMethod("MyMethod").MakeGenericMethod([Double]).Invoke($obj, "Test Message")
有输出
Generic type is System.String with argument Test Message
Generic type is System.Double with argument Test Message
MakeGenericMethod函数并不容易，特别是当该方法具有重载时更难处理。以下是来自该文章的复制粘贴代码：## Invoke-GenericMethod.ps1
## Invoke a generic method on a non-generic type:
##
## Usage:
##
## ## Load the DLL that contains our class
## [Reflection.Assembly]::LoadFile("c:\temp\GenericClass.dll")
##
## ## Invoke a generic method on a non-generic instance
## $nonGenericClass = New-Object NonGenericClass
## Invoke-GenericMethod $nonGenericClass GenericMethod String "How are you?"
##
## ## Including one with multiple arguments
## Invoke-GenericMethod $nonGenericClass GenericMethod String ("How are you?",5)
##
## ## Ivoke a generic static method on a type
## Invoke-GenericMethod ([NonGenericClass]) GenericStaticMethod String "How are you?"
##
param(
$instance = $(throw "Please provide an instance on which to invoke the generic method"),
[string] $methodName = $(throw "Please provide a method name to invoke"),
[string[]] $typeParameters = $(throw "Please specify the type parameters"),
[object[]] $methodParameters = $(throw "Please specify the method parameters")
)
## Determine if the types in $set1 match the types in $set2, replacing generic
## parameters in $set1 with the types in $genericTypes
function ParameterTypesMatch([type[]] $set1, [type[]] $set2, [type[]] $genericTypes)
{
$typeReplacementIndex = 0
$currentTypeIndex = 0
## Exit if the set lengths are different
if($set1.Count -ne $set2.Count)
{
return $false
}
## Go through each of the types in the first set
foreach($type in $set1)
{
## If it is a generic parameter, then replace it with a type from
## the $genericTypes list
if($type.IsGenericParameter)
{
$type = $genericTypes[$typeReplacementIndex]
$typeReplacementIndex++
}
## Check that the current type (i.e.: the original type, or replacement
## generic type) matches the type from $set2
if($type -ne $set2[$currentTypeIndex])
{
return $false
}
$currentTypeIndex++
}
return $true
}
## Convert the type parameters into actual types
[type[]] $typedParameters = $typeParameters
## Determine the type that we will call the generic method on. Initially, assume
## that it is actually a type itself.
$type = $instance
## If it is not, then it is a real object, and we can call its GetType() method
if($instance -isnot "Type")
{
$type = $instance.GetType()
}
## Search for the method that:
## - has the same name
## - is public
## - is a generic method
## - has the same parameter types
foreach($method in $type.GetMethods())
{
# Write-Host $method.Name
if(($method.Name -eq $methodName) -and
($method.IsPublic) -and
($method.IsGenericMethod))
{
$parameterTypes = @($method.GetParameters() | % { $_.ParameterType })
$methodParameterTypes = @($methodParameters | % { $_.GetType() })
if(ParameterTypesMatch $parameterTypes $methodParameterTypes $typedParameters)
{
## Create a closed representation of it
$newMethod = $method.MakeGenericMethod($typedParameters)
## Invoke the method
$newMethod.Invoke($instance, $methodParameters)
return
}
}
}
## Return an error if we couldn't find that method
throw "Could not find method $methodName"
public static string MyMethod<T>(T anArgument)
{
return string.Format( "Generic type is {0} with argument {1}",
typeof(T), anArgument.ToString());
}
Add-Type @'
using System.Linq;
public class Zipper
{
public static object[] Zip(object[] first, object[] second)
{
return first.Zip(second, (f,s) => new { f , s}).ToArray();
}
}
'@
$a = 1..4;
[string[]]$b = "a","b","c","d";
[Zipper]::Zip($a, $b);
f s
- -
1 a
2 b
3 c
4 d
我相信有更好的PowerShell方法来“压缩”两个数组，但你明白了我的意思。这里我回避了一个真正的挑战：在C#类中硬编码第三个参数到Zip，这样我就不必想办法传递Func<T1, T2, TResult>（也许也有一种PowerShell的方法可以做到这一点？）。
如果没有名称冲突，可以采用快速的方法：
[Sample]::"MyMethod"("arg")
[Sample]::MyMethod[string]("测试消息");。 - Granger