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V3124. Appending an element and checking for key uniqueness is performed on two different variables.
The analyzer detected a suspicious code fragment where a key is tested for being present in one dictionary, while the new element is appended to another. This situation may indicate a typo or a logic error.
Consider the following example:
Dictionary<string, string> dict = new Dictionary<string, string>();
Dictionary<string, string> _dict = new Dictionary<string, string>();
....
void Add(string key, string val)
{
if (!dict.ContainsKey(key))
_dict.Add(key, val);
}There may be two programming mistakes at once here. The first mistake has to do with appending an element to a wrong dictionary, which may distort the program's logic. The second deals with checking if the 'key' key is present in the 'dict' dictionary instead of '_dict'. If '_dict' already contains a value associated with the 'key' key, an 'ArgumentException' will be thrown when executing the '_dict.Add(key, val)' statement. There are two ways to fix this construct (both imply that the key is tested for the same dictionary the new element is appended to):
Dictionary<string, string> dict = new Dictionary<string, string>();
Dictionary<string, string> _dict = new Dictionary<string, string>();
....
void Add1(string key, string val)
{
if (!_dict.ContainsKey(key))
_dict.Add(key, val);
}
...
void Add2(string key, string val)
{
if (!dict.ContainsKey(key))
dict.Add(key, val);
}Was this page helpful?
