GenericMethods.ps1
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## 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) ## ## ## Invoke a generic static method on a type ## Invoke-GenericMethod ([NonGenericClass]) GenericStaticMethod String "How are you?" Function Invoke-GenericMethod { 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" } |