Exceptions running the finished app.

[jvsca]

Type of issue

Code doesn't work

Description

1. In finished app, several Possible null:

   static int Main(string[] args)
   {
       Option<FileInfo> fileOption = new("--file")
       {
           Description = "An option whose argument is parsed as a FileInfo",
           Required = true,
           DefaultValueFactory = result =>
           {
               if (result.Tokens.Count == 0)
               {
                   return new FileInfo("sampleQuotes.txt");
   
               }
               string filePath = result.Tokens.Single().Value;
               if (!File.Exists(filePath))
               {
                   result.AddError("File does not exist");
                   return null;                        // ⚠️ CS8603: Possible null reference return.
               }
               else
               {
                   return new FileInfo(filePath);
               }
           }
       };
   
       ...
   
       readCommand.SetAction(parseResult => ReadFile(
           parseResult.GetValue(fileOption),           // ⚠️ CS8603: Possible null argument for parameter 'file' in 'void Program.ReadFile(FileInfo file, ...)'.
           parseResult.GetValue(delayOption),
           parseResult.GetValue(fgcolorOption),
           parseResult.GetValue(lightModeOption)));
   
       deleteCommand.SetAction(parseResult => DeleteFromFile(
           parseResult.GetValue(fileOption),           // ⚠️ CS8603: Possible null argument for parameter 'file' in 'void Program.DeleteFromFile(FileInfo file, ...)'.
           parseResult.GetValue(searchTermsOption)));  // ⚠️ CS8603: Possible null argument for parameter 'searchTerms' in 'void Program.DeleteFromFile(FileInfo file, ...)'.
   
       addCommand.SetAction(parseResult => AddToFile(
           parseResult.GetValue(fileOption),           // ⚠️ CS8603: Possible null argument for parameter 'file' in 'void Program.AddToFile(FileInfo file, ...)'.
           parseResult.GetValue(quoteArgument),        // ⚠️ CS8603: Possible null argument for parameter 'quote' in 'void Program.AddToFile(FileInfo file, ...)'.
           parseResult.GetValue(bylineArgument))       // ⚠️ CS8603: Possible null argument for parameter 'byline' in 'void Program.AddToFile(FileInfo file, ...)'.
           );

2. File Not Found Exception in ReadFile():

   scl quotes read --file nofile

   internal static void ReadFile(FileInfo file, int delay, ConsoleColor fgColor, bool lightMode)
   {
       Console.BackgroundColor = lightMode ? ConsoleColor.White : ConsoleColor.Black;
       Console.ForegroundColor = fgColor;
       foreach (string line in File.ReadLines(file.FullName)) // ❌ System.IO.FileNotFoundException: 'Could not find the file '...\nofile'.'
       {
           Console.WriteLine(line);
           Thread.Sleep(TimeSpan.FromMilliseconds(delay * line.Length));
       }
   }

   Note:

    fileOption.DefaultValueFactory is never executed.
   

3. IO Exception:

   scl quotes delete --search-terms David "You can do" Antoine "Perfection is achieved"

   internal static void DeleteFromFile(FileInfo file, string[] searchTerms)
   {
       Console.WriteLine("Deleting from file");
   
       var lines = File.ReadLines(file.FullName).Where(line => searchTerms.All(s => !line.Contains(s))); // ❌ System.IO.IOException: 'The process cannot access the file '...\sampleQuotes.txt' because it is being used by another process.'
       File.WriteAllLines(file.FullName, lines);
   }

   Solution:

       File.WriteAllLines(file.FullName, lines.ToList());

Page URL

https://learn.microsoft.com/en-us/dotnet/standard/commandline/get-started-tutorial

Content source URL

https://github.com/dotnet/docs/blob/main/docs/standard/commandline/get-started-tutorial.md

Document Version Independent Id

fa160b1d-66ed-8c5d-37cd-b7e02443e9f1

Platform Id

0f144444-1ce3-cdf7-87a6-c659d44e08d3

Article author

@tdykstra

Metadata

• ID: 7705dc41-7297-0807-7e9c-2e6548c26b84
• PlatformId: 0f144444-1ce3-cdf7-87a6-c659d44e08d3
• Service: dotnet-fundamentals

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