Invoke-GenericMethod.ps1
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#requires -Version 2.0 $methodLookup = @{} function Invoke-GenericMethod { <# .Synopsis Invokes Generic methods on .NET Framework types .DESCRIPTION Allows the caller to invoke a Generic method on a .NET object or class with a single function call. Invoke-GenericMethod handles identifying the proper method overload, parameters with default values, and to some extent, the same type conversion behavior you expect when calling a normal .NET Framework method from PowerShell. .PARAMETER InputObject The object on which to invoke an instance generic method. .PARAMETER Type The .NET class on which to invoke a static generic method. .PARAMETER MethodName The name of the generic method to be invoked. .PARAMETER GenericType One or more types which are specified when calling the generic method. For example, if a method's signature is "string MethodName<T>();", and you want T to be a String, then you would pass "string" or ([string]) to the Type parameter of Invoke-GenericMethod. .PARAMETER ArgumentList The arguments to be passed on to the generic method when it is invoked. The order of the arguments must match that of the .NET method's signature; named parameters are not currently supported. .EXAMPLE Invoke-GenericMethod -InputObject $someObject -MethodName SomeMethodName -GenericType string -ArgumentList $arg1,$arg2,$arg3 Invokes a generic method on an object. The signature of this method would be something like this (containing 3 arguments and a single Generic type argument): object SomeMethodName<T>(object arg1, object arg2, object arg3); .EXAMPLE $someObject | Invoke-GenericMethod -MethodName SomeMethodName -GenericType string -ArgumentList $arg1,$arg2,$arg3 Same as example 1, except $someObject is passed to the function via the pipeline. .EXAMPLE Invoke-GenericMethod -Type SomeClass -MethodName SomeMethodName -GenericType string,int -ArgumentList $arg1,$arg2,$arg3 Invokes a static generic method on a class. The signature of this method would be something like this (containing 3 arguments and two Generic type arguments): static object SomeMethodName<T1,T2> (object arg1, object arg2, object arg3); .INPUTS System.Object .OUTPUTS System.Object .NOTES Known issues: Ref / Out parameters and [PSReference] objects are currently not working properly, and I don't think there's a way to fix that from within PowerShell. I'll have to expand on the PSGenericTypes.MethodInvoker.InvokeMethod() C# code to account for that. #> [CmdletBinding(DefaultParameterSetName = 'Instance')] param ( [Parameter(Mandatory = $true, ValueFromPipeline = $true, ParameterSetName = 'Instance')] $InputObject, [Parameter(Mandatory = $true, ParameterSetName = 'Static')] [Type] $Type, [Parameter(Mandatory = $true)] [string] $MethodName, [Parameter(Mandatory = $true)] [Type[]] $GenericType, [Object[]] $ArgumentList ) process { switch ($PSCmdlet.ParameterSetName) { 'Instance' { $_type = $InputObject.GetType() $object = $InputObject $flags = [System.Reflection.BindingFlags] 'Instance, Public' } 'Static' { $_type = $Type $object = $null $flags = [System.Reflection.BindingFlags] 'Static, Public' } } if ($null -ne $ArgumentList) { $argList = $ArgumentList.Clone() } else { $argList = @() } $params = @{ Type = $_type BindingFlags = $flags MethodName = $MethodName GenericType = $GenericType ArgumentList = [ref]$argList } $hash = ([pscustomobject]$params).GetHashCode() if($methodLookup.Contains($hash)) { $method = $methodLookup[$hash] } else { $method = Get-GenericMethod @params $methodLookup.Add($hash,$method) } if ($null -eq $method) { Write-Error "No matching method was found" return } # I'm not sure why, but PowerShell appears to be passing instances of PSObject when $argList contains generic types. Instead of calling # $method.Invoke here from PowerShell, I had to write the PSGenericMethods.MethodInvoker.InvokeMethod helper code in C# to enumerate the # argument list and replace any instances of PSObject with their BaseObject before calling $method.Invoke(). return [PSGenericMethods.MethodInvoker]::InvokeMethod($method, $object, $argList) } # process } # function Invoke-GenericMethod function Get-GenericMethod { [CmdletBinding()] param ( [Parameter(Mandatory = $true)] [Type] $Type, [Parameter(Mandatory = $true)] [string] $MethodName, [Parameter(Mandatory = $true)] [Type[]] $GenericType, [ref] $ArgumentList, [System.Reflection.BindingFlags] $BindingFlags = [System.Reflection.BindingFlags]::Default, [switch] $WithCoercion ) if ($null -eq $ArgumentList.Value) { $originalArgList = @() } else { $originalArgList = @($ArgumentList.Value) } foreach ($method in $Type.GetMethods($BindingFlags)) { $argList = $originalArgList.Clone() if (-not $method.IsGenericMethod -or $method.Name -ne $MethodName) { continue } if ($GenericType.Count -ne $method.GetGenericArguments().Count) { continue } if (Test-GenericMethodParameters -MethodInfo $method -ArgumentList ([ref]$argList) -GenericType $GenericType -WithCoercion:$WithCoercion) { $ArgumentList.Value = $argList return $method.MakeGenericMethod($GenericType) } } if (-not $WithCoercion) { $null = $PSBoundParameters.Remove('WithCoercion') return Get-GenericMethod @PSBoundParameters -WithCoercion } } # function Get-GenericMethod function Test-GenericMethodParameters { [CmdletBinding()] param ( [System.Reflection.MethodInfo] $MethodInfo, [ref] $ArgumentList, [Parameter(Mandatory = $true)] [Type[]] $GenericType, [switch] $WithCoercion ) if ($null -eq $ArgumentList.Value) { $argList = @() } else { $argList = @($ArgumentList.Value) } $parameterList = $MethodInfo.GetParameters() $arrayType = $null $hasParamsArray = HasParamsArray -ParameterList $parameterList if ($parameterList.Count -lt $argList.Count -and -not $hasParamsArray) { return $false } $methodGenericType = $MethodInfo.GetGenericArguments() for ($i = 0; $i -lt $argList.Count; $i++) { $params = @{ ArgumentList = $argList ParameterList = $ParameterList WithCoercion = $WithCoercion RuntimeGenericType = $GenericType MethodGenericType = $methodGenericType Index = [ref]$i ArrayType = [ref]$arrayType } $isOk = TryMatchParameter @params if (-not $isOk) { return $false } } $defaults = New-Object System.Collections.ArrayList for ($i = $argList.Count; $i -lt $parameterList.Count; $i++) { if (-not $parameterList[$i].HasDefaultValue) { return $false } $null = $defaults.Add($parameterList[$i].DefaultValue) } # When calling a method with a params array using MethodInfo, you have to pass in the array; the # params argument approach doesn't work. if ($hasParamsArray) { $firstArrayIndex = $parameterList.Count - 1 $lastArrayIndex = $argList.Count - 1 $newArgList = $argList[0..$firstArrayIndex] $newArgList[$firstArrayIndex] = $argList[$firstArrayIndex..$lastArrayIndex] -as $arrayType $argList = $newArgList } $ArgumentList.Value = $argList + $defaults.ToArray() return $true } # function Test-GenericMethodParameters function TryMatchParameter { param ( [System.Reflection.ParameterInfo[]] $ParameterList, [object[]] $ArgumentList, [Type[]] $MethodGenericType, [Type[]] $RuntimeGenericType, [switch] $WithCoercion, [ref] $Index, [ref] $ArrayType ) $params = @{ ParameterType = $ParameterList[$Index.Value].ParameterType RuntimeType = $RuntimeGenericType GenericType = $MethodGenericType } $runtimeType = Resolve-RuntimeType @params if ($null -eq $runtimeType) { throw "Could not determine runtime type of parameter '$($ParameterList[$Index.Value].Name)'" } $isParamsArray = IsParamsArray -ParameterInfo $ParameterList[$Index.Value] if ($isParamsArray) { $ArrayType.Value = $runtimeType $runtimeType = $runtimeType.GetElementType() } do { $isOk = TryMatchArgument @PSBoundParameters -RuntimeType $runtimeType if (-not $isOk) { return $false } if ($isParamsArray) { $Index.Value++ } } while ($isParamsArray -and $Index.Value -lt $ArgumentList.Count) return $true } function TryMatchArgument { param ( [System.Reflection.ParameterInfo[]] $ParameterList, [object[]] $ArgumentList, [Type[]] $MethodGenericType, [Type[]] $RuntimeGenericType, [switch] $WithCoercion, [ref] $Index, [ref] $ArrayType, [Type] $RuntimeType ) $argValue = $ArgumentList[$Index.Value] $argType = Get-Type $argValue $isByRef = $RuntimeType.IsByRef if ($isByRef) { if ($ArgumentList[$Index.Value] -isnot [ref]) { return $false } $RuntimeType = $RuntimeType.GetElementType() $argValue = $argValue.Value $argType = Get-Type $argValue } $isNullNullable = $false while ($RuntimeType.FullName -like 'System.Nullable``1*') { if ($null -eq $argValue) { $isNullNullable = $true break } $RuntimeType = $RuntimeType.GetGenericArguments()[0] } if ($isNullNullable) { continue } if ($null -eq $argValue) { return -not $RuntimeType.IsValueType } else { if ($argType -ne $RuntimeType) { $argValue = $argValue -as $RuntimeType if (-not $WithCoercion -or $null -eq $argValue) { return $false } } if ($isByRef) { $ArgumentList[$Index.Value].Value = $argValue } else { $ArgumentList[$Index.Value] = $argValue } } return $true } function HasParamsArray([System.Reflection.ParameterInfo[]] $ParameterList) { return $ParameterList.Count -gt 0 -and (IsParamsArray -ParameterInfo $ParameterList[-1]) } function IsParamsArray([System.Reflection.ParameterInfo] $ParameterInfo) { return @($ParameterInfo.GetCustomAttributes([System.ParamArrayAttribute], $true)).Count -gt 0 } function Resolve-RuntimeType { [CmdletBinding()] param ( [Parameter(Mandatory = $true)] [Type] $ParameterType, [Parameter(Mandatory = $true)] [Type[]] $RuntimeType, [Parameter(Mandatory = $true)] [Type[]] $GenericType ) if ($ParameterType.IsByRef) { $elementType = Resolve-RuntimeType -ParameterType $ParameterType.GetElementType() -RuntimeType $RuntimeType -GenericType $GenericType return $elementType.MakeByRefType() } elseif ($ParameterType.IsGenericParameter) { for ($i = 0; $i -lt $GenericType.Count; $i++) { if ($ParameterType -eq $GenericType[$i]) { return $RuntimeType[$i] } } } elseif ($ParameterType.IsArray) { $arrayType = $ParameterType $elementType = Resolve-RuntimeType -ParameterType $ParameterType.GetElementType() -RuntimeType $RuntimeType -GenericType $GenericType if ($ParameterType.GetElementType().IsGenericParameter) { $arrayRank = $arrayType.GetArrayRank() if ($arrayRank -eq 1) { $arrayType = $elementType.MakeArrayType() } else { $arrayType = $elementType.MakeArrayType($arrayRank) } } return $arrayType } elseif ($ParameterType.ContainsGenericParameters) { $genericArguments = $ParameterType.GetGenericArguments() $runtimeArguments = New-Object System.Collections.ArrayList foreach ($argument in $genericArguments) { $null = $runtimeArguments.Add((Resolve-RuntimeType -ParameterType $argument -RuntimeType $RuntimeType -GenericType $GenericType)) } $definition = $ParameterType if (-not $definition.IsGenericTypeDefinition) { $definition = $definition.GetGenericTypeDefinition() } return $definition.MakeGenericType($runtimeArguments.ToArray()) } else { return $ParameterType } } function Get-Type($object) { if ($null -eq $object) { return $null } return $object.GetType() } Add-Type -ErrorAction Stop -TypeDefinition @' namespace PSGenericMethods { using System; using System.Reflection; using System.Management.Automation; public static class MethodInvoker { public static object InvokeMethod(MethodInfo method, object target, object[] arguments) { if (method == null) { throw new ArgumentNullException("method"); } object[] args = null; if (arguments != null) { args = (object[])arguments.Clone(); for (int i = 0; i < args.Length; i++) { PSObject pso = args[i] as PSObject; if (pso != null) { args[i] = pso.BaseObject; } PSReference psref = args[i] as PSReference; if (psref != null) { args[i] = psref.Value; } } } object result = method.Invoke(target, args); for (int i = 0; i < arguments.Length; i++) { PSReference psref = arguments[i] as PSReference; if (psref != null) { psref.Value = args[i]; } } return result; } } } '@ |