Powershell - Why System.String method invocation fails on string literals?

Question

On a powershell session I tried to invoke some System.String methods for string literals, but them failed

I Tried

"ssz"::EndsWith("z")

but it failed with this message error : Method invocation failed because [System.String] does not contain a method named 'EndsWith'.

Then I tried with another System.String method

"ssz"::Substring(2,1)

but it failed too with error message Method invocation failed because [System.String] does not contain a method named 'Substring'.

To explore literal members I tried

"ssz"|Get-Member

and I got entries for EndsWith and Substring methods. This is the output. (I marked entries for my target methods)

I have .Net (c#) experience, and I read that powershell is the best choice to use/consume code implemented in .Net custom assemblies from OS scripts without compiling .net code. I can't figure out where is my mistake or misconception. ¿Can anyone explaint me why my code fails?

Thank you

The OS is Windows Server 2019

PowerShell Version Info

PS C:\> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      5.1.17763.2931
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17763.2931
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Answer 1

That's not a static method. Static example [string]::equals('a','a') Tab completion works after both :: and . . Powershell is a nice way to explore .Net.

[string]::equals  # see definitions without parentheses

OverloadDefinitions
-------------------
static bool Equals(string a, string b)
static bool Equals(string a, string b, System.StringComparison comparisonType)
static bool Equals(System.Object objA, System.Object objB)


[string]::equals('a','a')

True


Set-PSReadLineKeyHandler tab complete
[string]:: # tab — static examples

Empty               Concat              Format              IsNullOrEmpty       new
Compare             Copy                Intern              IsNullOrWhiteSpace  ReferenceEquals
CompareOrdinal      Equals              IsInterned          Join

Instance examples, including EndsWith()

'a'. # tab

Length            GetType           PadLeft           ToChar            ToLowerInvariant  ToUpperInvariant
Clone             GetTypeCode       PadRight          ToCharArray       ToSByte           Trim
CompareTo         IndexOf           Remove            ToDateTime        ToSingle          TrimEnd
Contains          IndexOfAny        Replace           ToDecimal         ToString          TrimStart
CopyTo            Insert            Split             ToDouble          ToType            Chars
EndsWith          IsNormalized      StartsWith        ToInt16           ToUInt16
Equals            LastIndexOf       Substring         ToInt32           ToUInt32
GetEnumerator     LastIndexOfAny    ToBoolean         ToInt64           ToUInt64
GetHashCode       Normalize         ToByte            ToLower           ToUpper


'a'.endswith

OverloadDefinitions
-------------------
bool EndsWith(string value)
bool EndsWith(string value, System.StringComparison comparisonType)
bool EndsWith(string value, bool ignoreCase, cultureinfo culture)


'abc'.endswith('Bc') # case sensitive

False


'abc'.endswith('Bc', 'OrdinalIgnoreCase')

True


'abc'.endswith('Bc', ($ignoreCase=$true), $PSCulture)

True


'abc' -like '*Bc'  # or make it easy

True

Answer 2

You are completely fine. Just that the method to call is using DOT and not double colon:

Try these replacing yours:

"ssz".EndsWith("z")
"ssz".Substring(2,1)

Hope it helps :)

Answer 3

To complement the existing, helpful answers:

• Use ., the member-access operator aka dot notation to access instance members of a given object.

  • This is the same syntax as in many other languages.

• Use ::, the static member operator, to access static members, i.e. class-level members.

  • This syntax is peculiar to PowerShell.

  • It is typically applied to type literals (e.g. [string]) rather than to instances (e.g., "ssz"), but can be applied to either.

    • E.g., [string]::IsNullOrEmpty('') and (somewhat confusingly) "ssz"::IsNullOrEmpty('') are equivalent and both return $true.

  • For more information about type literals in PowerShell, see this answer.

  • Of syntactic necessity, PowerShell requires a distinct operator for accessing static members, because type literals are objects themselves, namely instances of System.Reflection.TypeInfo, so that using . accesses the latter's instance properties; e.g., [string].FullName returns the type's namespace-qualified name.