如何在catch块c＃中管理异常？

Question

I have following code.

try
{
    int s=10;
    int k=0;
    int stdsd = s / k;
}
catch (DivideByZeroException ext)
{
    FileStream fs = new FileStream(@"C:\temp\data.txt", FileMode.Open);  
    //encountered an exception as file doesn't exist.
}
catch (Exception ex)
{
}
finally
{
    //some code here.
}

In above code when exception occured then it will try to write that in one file in catch block.but when it trying to open that file that file doen't exists, so in such cases system crashed. I want to execute such critical code in finally block but due to exception in catch block it not going further to that line.

I know we can check file exists check but I don't want to check file exist check over here, I want to how to manage that in catch block. can please assist the best way to manage exception in catch block.

Answer 1

You can't handle the exception generated from one catch block in a catch block associated with the same try/catch statement. Instead, you need an extra one:

catch (DivideByZeroException ext)
{
    try
    {
        FileStream fs = new FileStream(@"C:\temp\data.txt", FileMode.Open);  
    }
    catch (IOException e)
    {
        // Handle the exception here
    }
}

Note that you should be using a using statement when opening the stream, so that you'll close it automatically whether or not an exception is thrown later.

I'd also recommend not having the code like this in the catch block directly - typically catch blocks should be short, for readability. Consider moving all the error-handling functionality into a separate method (or possibly even a separate class).

Answer 2

Just use another try {} catch {} ...

try { 
    // ...
    try {
        // try opening your file here ...
    } catch (Exception) {
        // ...
    }
} catch (Exception) {
    // ...
}

Answer 3

If you don't want to check the existence of the file "over here" (in the exception), then you could alternatively check the existence "over there", that is: earlier in the code.

What you want to do is to write an exception log to a file, as I understand it. So you could configure the correct log file handling earlier in the code, in the best case with a good log file handler. After this the only thing you have to do within the exception handler is to push your exception message to the log handler - which will then write this information properly to the file.

Answer 4

exceptions are very powerful future of any language that can not be ignored in most cases , but try to avoid it if possible

Look at this

            String File = "File.txt";
            System.IO.FileInfo fileinfo = new System.IO.FileInfo(File);

           if(fileinfo.Exists)
           {
               using (System.IO.FileStream file = new System.IO.FileStream(File, System.IO.FileMode.Open, System.IO.FileAccess.ReadWrite))
             {
                 // operation on file here
             }
           }else
           {
               using (System.IO.FileStream file = new System.IO.FileStream(File, System.IO.FileMode.OpenOrCreate, System.IO.FileAccess.ReadWrite))
               {
                   // operation on file here now the file is new file 
               }
           }