Not all code paths return a value although I do have returns?

Question

I'm trying to return some fields (e.g. cellPhone, mainAddress, cityStateZip, serverSetup) from below function based on input, and I have implemented an interesting switch statement, but clearly I'm returning a string in all cases.

public static string JsonToObjects(bool Enumerate, string jsonInputFile)
{
    string inputFile = Path.GetFileName(jsonInputFile); // Return File Name + Extension
    var lines = GetLines(File.ReadAllText(jsonInputFile));
    var groups = lines.GroupByProximity(0.12);
    var lookup = groups.ToLookup(g => g.First().Text, g => g.Skip(1).Select(line => line.Text));
    var serverSetup = lookup["Server Setup"]
        .First().SkipWhile(s => s.ToString().ToUpper() != "V").Skip(1).FirstOrDefault();

    switch (Enumerate)
    {
        case true:
            Log("\nEnumerating JSON items...\n");
            
            var cellPhone = lookup["Cell Phone"].First().FirstOrDefault();
            var mainAddress = lookup["Main Address"].First().FirstOrDefault();
            var cityStateZip = lookup["City / State / Zip"].First().FirstOrDefault();

            Log(cellPhone);
            Log(mainAddress);
            Log(cityStateZip);
            Log(serverSetup);

            Log("\n");

            var pairs = lines.SkipWhile(l => l.Text != "Practice Name").Pairs();

            // Ingest the lines in pairs and setup the values to go out into the CSV.
            foreach (var pair in pairs)
            {
                Log($"{pair.Key}: {pair.Value}");
                return $"{pair.Key}: {pair.Value}";
            }

            break;
        case false:
            Log("Using Cho Package...");

            using (var p = new ChoJSONReader(jsonInputFile).WithJSONPath("$..readResults")) // "readResults": [
            {
                p.Where(r1 => r1.page == 1)
                .Select(r1 =>
                {
                    var lines = (dynamic[])r1.lines;
                    return new
                    {
                        FileName = inputFile,
                        Page = r1.page,
                        CellPhone = //lines[12].text,
                            fieldValue(lines, "Cell Phone"),
                        //cellPhone,
                        MainAddress = //lines[16].text,
                            fieldValue(lines, "Main Address"),
                        //mainAddress,
                        CityStateZip = //lines[18].text,
                            fieldValue(lines, "City / State / Zip"),
                        //cityStateZip,
                        ServerSetup = serverSetup
                    };
                }
                );
            }
            break;
        default:
            Log("Default case");
            return "Default case";
            break;
    }
}

Why then am I still getting an error:

"Not all code paths return a value"

Answer 1

Either change every break in your switch so that it is a return (if you will vary what you return based on whether the true or the false case is applied) or put a return statement at the end of your method, after your switch is finished with

The compiler isn't kidding; it really can see paths through your code that don't end in a return. You can trace them too.. follow your true case.. it can reach break, exit the switch and then have no return statement before it hits the end of the method. You might be certain that pairs will definitely always have a value but the compiler doesn't have that same level of knowledge about the program as you and it doesn't trace back to try and find evidence that pairs will always have a value.. it just sees "return statement inside a loop which is a block that might not execute, means code might not hit that return statement"

In case you're under an illusion as to what default is for, in a switch.. it is used when no other case applies. It is not "something that runs every time, regardless of whether some other case applied or not" so it can't be used as a catch all to return something if other cases didn't

If you're certain that one of your returns in the switch will be hit you can return something useless at the end of the method or better, throw an exception with a meaningful message so that in 6 months when all these "None of the switch statements returned a value in JsonToObjects, the input values were..." start appearing in the logs you have a good pointer to what is going wrong and where. Do not make your error message "this should never be hit"