Examples of errors detected by the V3219 diagnostic

V3219. The variable was changed after it was captured in a LINQ method with deferred execution. The original value will not be used when the method is executed.

QuantConnect Lean

V3219 The 'lineNumber' variable was changed after it was captured in a LINQ method with deferred execution. The original value will not be used when the method is executed. FutureMarginBuyingPowerModelTests.cs 720

public void FutureMarginModel_MarginEntriesValid(string market)
{
  ....
  var lineNumber = 0;
  var errorMessageTemplate = $"Error encountered in file
                               {marginFile.Name} on line ";
  var csv = File.ReadLines(marginFile.FullName)
                .Where(x =>    !x.StartsWithInvariant("#")
                            && !string.IsNullOrWhiteSpace(x))
                .Skip(1)
                .Select(x =>
  {
    lineNumber++;                                                  // <=

    ....
  });

  lineNumber = 0;                                                  // <=
  foreach (var line in csv)
  {
    lineNumber++;                                                  // <=
    ....
  }
}