Trying to convert a string to integer causes a error of type System.FormatException

Question

I am making a client for my server and I am stuck. My server is sending Unicode text, and my client recieves it. The problem is this piece of code:

Enum.GetName(typeof(FTPCommands), Convert.ToInt32(replace[0].Trim()))

I am trying to get the text from my Enum FTPCommands with the number the server sent me. First my client is recieving the ID: 1 732847823 (Result from the debugger).

It splits correctly, in this case: replace[0].ToString() -->"1" AND replace[1].ToString() -->"732847823"

No error occurs!

On the second command, the client is recieving an error from the server:

8 Server is too full, try again laiter

And it also splits correctly, in this case:

replace[0].ToString() -->"1" AND replace[0].ToString() -->"8" AND replace[1].ToString() -->"Server" AND replace[2].ToString() -->"is" AND replace[3].ToString() -->"too" AND replace[4].ToString() -->"full," AND replace[4].ToString() -->"try" AND replace[4].ToString() -->"again" AND replace[4].ToString() -->"laiter"

And now the error occurs! I dont know why this is working with the first command and not also with the command 8 . If I replace the replace[0].Trim() with the number 8 it works fine. What is wrong with the code, or what could cause that error? Is it because I am using Unicode?

Here are some samples of my code:

NetworkStream stream = client.GetStream();
                StreamWriter sw = new StreamWriter(stream, Encoding.Unicode);
                StreamReader sr = new StreamReader(stream);
                //SendFileToServer(@"\\fs1\home\manuel.boehmler\contacts.rar", client);
                AnswerToServer(FTPCommands.ID,null,sw);
                AnswerToServer(FTPCommands.Username, txtBUserName.Text, sw);
                AnswerToServer(FTPCommands.Password, txtBPassword.Text, sw);
                AnswerToServer(FTPCommands.login,null, sw);
                AnswerToServer(FTPCommands.MaxMbytes, txtBPassword.Text, sw);

                //AnswerToServer(FTPCommands.FileTransfer,"", sw);


                string line = null;
                while (client.Connected == true)
                {
                    if (!string.IsNullOrEmpty(line = sr.ReadLine()) && line.Length >= 2)
                    {

                        RichTxtMessage("Bekommt: " + line, true);
                        string[] replace = null;
                        string command = "";

    replace = line.Split(' ');
    command = replace[0].ToUpperInvariant();

    string arguments = replace.Length > 1 ? line.Substring(replace[0].Length + 1) : null;

    switch (Enum.GetName(typeof(FTPCommands), Convert.ToInt32(replace[0].Trim())).ToUpperInvariant()) //Error occurs here
    {
        case "ID":
          RichTxtMessage(arguments,true);
          break;
        case "ERROR":
          RichTxtMessage(arguments, true);
          break;
    }
}

public enum FTPCommands
{

    Persmission = 0,
    ID = 1,
    Username = 2,
    Password = 3,
    UserNameReq = 4,
    PasswordReq = 5,

    Chat = 6,
    MessageRecived = 7,
    Error = 8,
    Warning = 9
}

EDIT (UPDATE):

When Iam using UTF8 as encoding the console gives me this result back:

As you can see the wired symbols as first char. However it doesnt show me the symboles when Iam using UNICODE (but still not working). I solved the problem, I dont use any Encoding for my FTP-Server

Answer 1

Instead of Convert.ToInt32(replace[0].Trim())) use int.TryParse:

int i = 0;
int.TryParse(replace[0].Trim(), out i)

Edit: If null was in an element, that element cannot be converted as int and it will throw error

string arguments = replace.Length > 1 ? line.Substring(replace[0].Length + 1) : null;

switch (Enum.GetName(typeof(FTPCommands), Convert.ToInt32(replace[0].Trim())).ToUpperInvariant()) //Error occurs here

Assign some int instead of null, or check it is not null or empty before converting to int

  string arguments = replace.Length > 1 ? line.Substring(replace[0].Length + 1) : "-1";

// OR do this
int opt = 0;
if (!string.IsNullOrEmpty(replace[0].Trim())
opt = int.TryParse(replace[0].Trim(), out opt);
switch (Enum.GetName(typeof(FTPCommands), Convert.ToInt32(opt)).ToUpperInvariant())       //Error occurs here

Answer 2

I am not sure why you are bothering to convert the integer to a string. You could just cast to the enum and use switch with just enum values, eg

int id = -1;
if (int.TryParse (replace[0].Trim (), id))
{
    switch ((FTPCommands)id)
    {
        case FTPCommands.ID:
            RichTxtMessage(arguments,true);
            break;
        case FTPCommands.Error:   
            RichTxtMessage(arguments, true);
            break;
    }
}