sln-add: Don't add solution folders with invalid chars

Author: edvilme

src/Cli/dotnet/commands/dotnet-sln/add/Program.cs

@@ -31,6 +31,13 @@ private static string GetSolutionFolderPathWithForwardSlashes(string path)
             return "/" + string.Join("/", PathUtility.GetPathWithDirectorySeparator(path).Split(Path.DirectorySeparatorChar, StringSplitOptions.RemoveEmptyEntries)) + "/";
         }
 
+        private static bool DoesSolutionFolderPathContainInvalidChars(string pathFragment)
+        {
+            return pathFragment
+                .Split(Path.DirectorySeparatorChar)
+                .Any(pathFragment => pathFragment == ".." || pathFragment == "." || Path.GetInvalidFileNameChars().Any(c => pathFragment.Contains(c)));
+        }
+
         public AddProjectToSolutionCommand(ParseResult parseResult) : base(parseResult)
         {
             _fileOrDirectory = parseResult.GetValue(SlnCommandParser.SlnArgument);
@@ -82,15 +89,10 @@ private async Task AddProjectsToSolutionAsync(string solutionFileFullPath, IEnum
                 {
                     Encoding = new UTF8Encoding(encoderShouldEmitUTF8Identifier: true)
                 });
+
                 // Set default configurations and platforms for sln file
-                foreach (var platform in _defaultPlatforms)
-                {
-                    solution.AddPlatform(platform);
-                }
-                foreach (var buildType in _defaultBuildTypes)
-                {
-                    solution.AddBuildType(buildType);
-                }
+                _defaultPlatforms.ToList().ForEach(solution.AddPlatform);
+                _defaultBuildTypes.ToList().ForEach(solution.AddBuildType);
             }
 
             SolutionFolderModel? solutionFolder = (!_inRoot && !string.IsNullOrEmpty(_solutionFolderPath))
@@ -100,9 +102,9 @@ private async Task AddProjectsToSolutionAsync(string solutionFileFullPath, IEnum
             foreach (var projectPath in projectPaths)
             {
                 string relativePath = Path.GetRelativePath(Path.GetDirectoryName(solutionFileFullPath), projectPath);
-                // Add fallback solution folder if relative path does not contain `..`.
-                string relativeSolutionFolder =  relativePath.Split(Path.DirectorySeparatorChar).Any(p => p == "..")
-                    ? string.Empty : Path.GetDirectoryName(relativePath);
+
+                // Add fallback solution folder if relative path does not contain invalid characters
+                string relativeSolutionFolder = DoesSolutionFolderPathContainInvalidChars(projectPath) ? string.Empty : Path.GetDirectoryName(relativePath);
 
                 if (!_inRoot && solutionFolder is null && !string.IsNullOrEmpty(relativeSolutionFolder))
                 {