Playing around with C# encryption

Been trying to venture out and learn some C# and powershell, giving myself little projects to try and learn. Recently I have been trying to convert some code from powershell to C# and I believe I got it working but am coming across some errors creating the IV for RijndaelManaged.

This is the powershell code that works fine, pulled from the internet

function Decrypt-String($Encrypted, $Passphrase, $salt, $init="Yet another key")
{
   if($Encrypted -is [string]){
      $Encrypted = [Convert]::FromBase64String($Encrypted)
   }
   $r = new-Object System.Security.Cryptography.RijndaelManaged
   $pass = [System.Text.Encoding]::UTF8.GetBytes($Passphrase)
   $salt = [System.Text.Encoding]::UTF8.GetBytes($salt)

   $r.Key = (new-Object Security.Cryptography.PasswordDeriveBytes $pass, $salt, "SHA1", 5).GetBytes(32) #256/8

   $r.IV = (new-Object Security.Cryptography.SHA1Managed).ComputeHash( [Text.Encoding]::UTF8.GetBytes($init) )[0..15]

   $d = $r.CreateDecryptor()
   $ms = new-Object IO.MemoryStream @(,$Encrypted)
   $cs = new-Object Security.Cryptography.CryptoStream $ms,$d,"Read"

   $sr = new-Object IO.StreamReader $cs
   Write-Output $sr.ReadToEnd()
   $sr.Close()
   $cs.Close()
   $ms.Close()
   $r.Clear()
}

And this is the C# code i moved it over to

public static string Decrypt_String(string cipherText, string passPhrase, string Salt)
{
    string hashAlgorithm = "SHA1";
    int passwordIterations = 5;
    initName = "Yet another key";
    using (RijndaelManaged r = new RijndaelManaged())
    {
        byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
        byte[] PassPhraseBytes = Encoding.UTF8.GetBytes(passPhrase);
        byte[] SaltBytes = Encoding.UTF8.GetBytes(Salt);
        byte[] initVectorBytes = Encoding.UTF8.GetBytes(initName);

        PasswordDeriveBytes password = new PasswordDeriveBytes(PassPhraseBytes,SaltBytes,hashAlgorithm,passwordIterations);
        byte[] keyBytes = password.GetBytes(32); //(256 / 32)
        r.Key = keyBytes;

        SHA1Managed cHash = new SHA1Managed();
        r.IV = cHash.ComputeHash(Encoding.UTF8.GetBytes(initName),0,16);

        ICryptoTransform decryptor = r.CreateDecryptor();
        MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
        CryptoStream cryptoStream = new CryptoStream(memoryStream,
                                                  decryptor,
                                                  CryptoStreamMode.Read);
        StreamReader streamReader = new StreamReader(cryptoStream);
        string output = streamReader.ReadToEnd();
        return output;
    }


}

Currently the ComputeHash is spitting back an error telling me the value is invalid. here are the values I am using from the working encrypt function

cipherText = "s6ZqNpJq05jsMh2+1BxZzJQDDiJGRQPqIYzBjYQHsgw="

saltValue = "}=[BJ8%)vjJDnQfmvC))))3Q"

passphrase = "S@lt3d"

Any ideas on why the IV wont set properly?

EDIT: Sorry the exception is

Line 38:             r.IV = cHash.ComputeHash(initVectorBytes, 0, 16);

Exception Details: System.ArgumentException: Value was invalid.

Kind of generic