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I’m building a new program, but when I run it, an error pops up. The error displayed is as follows:
You cannot call a method on a null-valued expression.
At C:\Users\xxx\Downloads\md5sum.ps1:6 char:29
+ $hash = [System.BitConverter]::ToString($md5.Compute ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNullI have tried several workarounds, but they still do not get the desired results. If you have come across this situation and have a solution for the “you cannot call a method on a null valued expression in powershell” problem, pls let me know. Here is what I do:
$answer = Read-Host "File name and extension (ie; file.exe)"
$someFilePath = "C:\Users\xxx\Downloads\$answer"
If (Test-Path $someFilePath){
$stream = [System.IO.File]::Open("$someFilePath",[System.IO.Filemode]::Open, [System.IO.FileAccess]::Read)
$hash = [System.BitConverter]::ToString($md5.ComputeHash($stream))
$hash
$stream.Close()
}
Else{
Write-Host "Sorry, file $answer doesn't seem to exist."
}Thanks!
This is because you have an undeclared variable (null). It is This error occurred because you tried to execute a method which does not exist. The null-valued expression was $md5. This must be declared in another place than the one you have commented on.$md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProviderPS C:\Users\Matt> $md5 | gm
TypeName: System.Security.Cryptography.MD5CryptoServiceProvider
Name MemberType Definition
---- ---------- ----------
Clear Method void Clear()
ComputeHash Method byte[] ComputeHash(System.IO.Stream inputStream), byte[] ComputeHash(byte[] buffer), byte[] ComputeHash(byte[] buffer, int offset, ....ComputeHash() from $md5.ComputeHash(). The same effect could be achieved by typing gibberish.PS C:\Users\Matt> $bagel.MakeMeABagel()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $bagel.MakeMeABagel()
+ ~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
The cause: You have an undeclared variable (null). It is
$md5. This must be declared in another place than the one you have commented on.This error occurred because you tried to execute a method which does not exist.
Solution: The null-valued expression was
.ComputeHash()from$md5.ComputeHash(). The same effect could be achieved by typing gibberish.