Our website uses cookies to enhance your browsing experience.
Accept
to the top
close form

Fill out the form in 2 simple steps below:

Your contact information:

Step 1
Congratulations! This is your promo code!

Desired license type:

Step 2
Team license
Enterprise license
** By clicking this button you agree to our Privacy Policy statement
close form
Request our prices
New License
License Renewal
--Select currency--
USD
EUR
* By clicking this button you agree to our Privacy Policy statement

close form
Free PVS‑Studio license for Microsoft MVP specialists
* By clicking this button you agree to our Privacy Policy statement

close form
To get the licence for your open-source project, please fill out this form
* By clicking this button you agree to our Privacy Policy statement

close form
I am interested to try it on the platforms:
* By clicking this button you agree to our Privacy Policy statement

close form
check circle
Message submitted.

Your message has been sent. We will email you at


If you do not see the email in your inbox, please check if it is filtered to one of the following folders:

  • Promotion
  • Updates
  • Spam

>
>
>
V3191. Iteration through collection mak…
menu mobile close menu
Analyzer diagnostics
General Analysis (C++)
General Analysis (C#)
General Analysis (Java)
Micro-Optimizations (C++)
Diagnosis of 64-bit errors (Viva64, C++)
Customer specific requests (C++)
MISRA errors
AUTOSAR errors
OWASP errors (C#)
Problems related to code analyzer
Additional information
toggle menu Contents

V3191. Iteration through collection makes no sense because it is always empty.

Jun 30 2023

The analyzer has detected an attempt to iterate through an empty collection. This operation makes no sense: probably, there is an error in the code.

Let's look at the example:

private List<Action> _actions;
....
public void Execute()
{
  var remove = new List<Action>();
  foreach (var action in _actions)
  {
    try
    {
      action.Invoke();
    }
    catch (Exception ex)
    {
      Logger.LogError(string.Format("Error invoking action:\n{0}", ex));
    }
  }
  foreach (var action in remove)
    _actions.Remove(action);
}

The 'Execute' method invokes delegates from the '_actions' list one by one. It also catches and logs errors that occur during the method execution. In addition to the main loop, there is another one at the end of the method. The loop should remove the delegates that are stored in the 'remove' collection from the '_actions' list.

The issue is that the 'remove' collection will always be empty. It is created at the beginning of the method, but is not filled during the method's execution. Thus, the last loop will never be executed.

The correct method's implementation may look like this:

public void Execute()
{
  var remove = new List<Action>();
  foreach (var action in _actions)
  {
    try
    {
      action.Invoke();
    }
    catch (Exception ex)
    {
      Logger.LogError(string.Format("Error invoking action:\n{0}", ex));
      remove.Add(action);
    }
  }
  foreach (var action in remove)
    _actions.Remove(action);
}

Now we add the delegates that caused exceptions to the 'remove' collection, so that we can remove them later.

The analyzer may issue a warning for a method call that iterates through a collection.

Look at another example:

int ProcessValues(int[][] valuesCollection,
                  out List<int> extremums)
{
  extremums = new List<int>();

  foreach (var values in valuesCollection)
  {
    SetStateAccordingToValues(values);
  }
  return extremums.Sum();
}

The 'ProcessValues' method takes arrays of numbers for processing. In this case, we are interested in the 'extremums' collection: it is created empty and is not filled during the method execution. 'ProcessValues' returns the result of calling the 'Sum' method on the 'extremums' collection. The code looks wrong because calling 'Sum' always returns 0.

The correct method's implementation may look as follows:

int ProcessValues(int[][] valuesCollection,
                  out List<int> extremums)
{
  extremums = new List<int>();

  foreach (var values in valuesCollection)
  {
    SetStateAccordingToValues(values);
    extremums.Add(values.Max());
  }
  return extremums.Sum();
}