CodeQL documentation

Container contents are never initialized

ID: cs/empty-collection
Kind: problem
Security severity: 
Severity: error
Precision: high
   - reliability
   - maintainability
   - useless-code
   - external/cwe/cwe-561
Query suites:
   - csharp-security-and-quality.qls

Click to see the query in the CodeQL repository

Code that queries the contents of a collection (such as ContainsKey or Count) is invoked on an object that is known to be empty. Such queries do not return interesting results, and may indicate missing code or a logic error.


Either remove the collection if it is unnecessary, or ensure that it contains the correct data.


The following example code is supposed to return the name of the day, but does not work because the collection daysOfWeek is never populated. When this code is run, an ArgumentOutOfRangeException exception is thrown.

class Calendar
    IList<string> daysOfWeek = new List<string>();

    public string dayName(int day)
        return daysOfWeek[day - 1];

This problem is fixed by populating the variable daysOfWeek with the correct data.

class CalendarFix
    IList<string> daysOfWeek = new List<string>

    public string dayName(int day)
        return daysOfWeek[day - 1];
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