LINQ Error IN ForEach

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 < filePaths.Length; 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 < filePaths.Length; 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 < fileheaders.Length; j++)
{
hdict[fileheaders[j]].Add(spline[j]);
}
foreach (string header in notfileheaders)
{
hdict[header].Add(null);
}
});
}

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Jaish Mathews8y ago
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.