file IO, is this a bug in Powershell?

Question

I have the following code in Powershell

$filePath = "C:\my\programming\Powershell\output.test.txt"

try
{
    $wStream = new-object IO.FileStream $filePath, [System.IO.FileMode]::Append, [IO.FileAccess]::Write, [IO.FileShare]::Read

    $sWriter = New-Object  System.IO.StreamWriter $wStream

    $sWriter.writeLine("test")
 }

I keep getting error:

Cannot convert argument "1", with value: "[IO.FileMode]::Append", for "FileStream" to type "System.IO.FileMode": "Cannot convert value "[IO.FileMode]::Append" to type "System.IO.FileMode" due to invalid enumeration values. Specify one of the following enumeration values and try again. The possible enumeration values are "CreateNew, Create, Open, OpenOrCreate, Truncate, Append"."

I tried the equivalent in C#,

    FileStream fStream = null;
    StreamWriter stWriter = null;

    try
    {
        fStream = new FileStream(@"C:\my\programming\Powershell\output.txt", FileMode.Append, FileAccess.Write, FileShare.Read);
        stWriter = new StreamWriter(fStream);
        stWriter.WriteLine("hahha");
    }

it works fine!

What's wrong with my powershell script? BTW I am running on powershell

Major  Minor  Build  Revision
-----  -----  -----  --------
3      2      0      2237

Answer 1

Another way would be to use just the name of the value and let PowerShell cast it to the target type:

New-Object IO.FileStream $filePath ,'Append','Write','Read'