LINQ Error IN ForEach

Question

Hi, I am trying to combile multiple csv files to one, getting error as - in code 'IEnumerable ' does not contain a definition for ' ForEach ' and no extension method 'ForEach' accepting a first argument of type 'IEnumerable ' could be found (are you missing a using directive or an assembly reference?) CODE - public static void CombineMisMatchedCsvFiles( string [] filePaths, string destinationFile, char splitter = ',' ) { HashSet string > combinedheaders = new HashSet string >(); int i; // aggregate headers for (i = 0; i { string file = filePaths[i]; combinedheaders.UnionWith(File.ReadLines(file).First().Split(splitter)); } var hdict = combinedheaders.ToDictionary(y => y, y => new List object >()); string [] combinedHeadersArray = combinedheaders.ToArray(); for (i = 0; i { var fileheaders = File.ReadLines(filePaths[i]).First().Split(splitter); var notfileheaders = combinedheaders.Except(fileheaders); File.ReadLines(filePaths[i]).Skip(1).Select(line => line.Split(splitter)). ForEach (spline => { for ( int j = 0; j { hdict[fileheaders[j]].Add(spline[j]); } foreach ( string header in notfileheaders) { hdict[header].Add( null ); } }); }

Jaish Mathews · Answer

It's an expected behaviour in C#. In C# you can't apply ForEach against a collection of "IEnumerable", but you need to add a separate loop using "GetEnumerator()". Your select query, "File.ReadLines(filePaths[i]).Skip(1). Select(.......... returns a type of IEnumerable and you are trying to run ForEach against it, which it can't understand. If you want it in a single line use it like below after converting to a List. File.ReadLines(filePaths[i]).Skip(1).Select(line => line.Split(splitter)) .ToList(). ForEach(spline => ............ Your error will disappear now, but please decide which approach is proper for you as I am only explaining the root cause of the error oyu mentioned.