V3002. The switch statement does not cover all values of the enum.

The analyzer has detected a 'switch' statement where selection is done for a variable of the enum type, some of the enumeration elements missing in the 'switch' statement. This may indicate an error.

Consider this example:

public enum Actions { Add, Remove, Replace, Move, Reset };
public void SomeMethod(Actions act)
{
  switch (act)
  {
    case Actions.Add:     Calculate(1); break;
    case Actions.Remove:  Calculate(2); break;
    case Actions.Replace: Calculate(3); break;
    case Actions.Move:    Calculate(5); break;
  }
}

The 'Actions' enumeration in this code contains 5 named constants, while the 'switch' statement, selecting among the values of this enumeration, only selects among 4 of them. This is very likely a mistake.

It may be that the programmer added a new constant during refactoring but forgot to add it into the list of cases in the 'switch' statement, or simply skipped it by mistake, as it sometimes happens with large enumerations. This results in incorrect processing of the missing value.

The correct version of this code should look like this:

public void SomeMethod(Actions act)
{
  switch (act)
  {
    case Actions.Add:     Calculate(1); break;
    case Actions.Remove:  Calculate(2); break;
    case Actions.Replace: Calculate(3); break;
    case Actions.Move:    Calculate(5); break;
    case Actions.Reset:   Calculate(6); break;
  }
}

Or this:

public void SomeMethod(Actions act)
{
  switch (act)
  {
    case Actions.Add:     Calculate(1); break;
    case Actions.Remove:  Calculate(2); break;
    case Actions.Replace: Calculate(3); break;
    case Actions.Move:    Calculate(5); break;
    default:              Calculate(10); break;
  }
}

The analyzer doesn't output the warning every time there are missing enumeration elements in the 'switch' statement; otherwise, there would be too many false positives. There are a number of empirical exceptions from this rule, the main of which are the following:

  • A default-branch is present;
  • The missing constant's name includes the words "None", "Unknown", and the like.
  • The missing constant is the very last in the enumeration and its name includes the words "end", "num", "count", and the like.
  • The enumeration consists of only 1 or 2 constants;
  • And so on.
You can look at examples of errors from real projects which were detected by this diagnostic message.

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