Should I dispose of manually a Dictionary data structure after I am done using it?

Question

Is it worth the effort to try and actively dispose of the Dictionary in this code, or just leave it to managed garbage collection?

private void LogReprocessTsk(List<ReprocessTsk> reprocessTsks)
{
    foreach (ReprocessTsk reprocessTsk in reprocessTsks)
    {
        Dictionary<string, string> logMessage = new Dictionary<string, string>
        {
            { "Message", "insert into REPROCESS_TSK - parentId changed" },
            { "TSKLOC", reprocessTsk.TSKLOC },
            { "CRS", reprocessTsk.CRS.ToString() },
            { "PROCESSED", reprocessTsk.PROCESSED.ToString() },
            { "OldParentId", reprocessTsk.OldParentId },
            { "NewParentId", reprocessTsk.NewParentId }
        };

        _logger.LogInformation(JsonConvert.SerializeObject(logMessage));
    }
}

Answer 1

The garbage collector does its job very well and there is no reason to force a premature garbage collection. The dictionary gets out of the scope of the loop anyway at each iteration and becomes automatically a candidate for garbage collection.

You can minimize the number of object creations if you declare only one dictionary before the loop and clear it after use.

var logMessage = new Dictionary<string, string>();
foreach (ReprocessTsk reprocessTsk in reprocessTsks) {
    logMessage.Add("Message", "insert into REPROCESS_TSK - parentId changed");
    logMessage.Add("TSKLOC", reprocessTsk.TSKLOC);
    logMessage.Add("CRS", reprocessTsk.CRS.ToString());
    logMessage.Add("PROCESSED", reprocessTsk.PROCESSED.ToString());
    logMessage.Add("OldParentId", reprocessTsk.OldParentId);
    logMessage.Add("NewParentId", reprocessTsk.NewParentId);

    _logger.LogInformation(JsonConvert.SerializeObject(logMessage));
    logMessage.Clear();
}

Since you are using the same keys at each foreach iteration, yet another possibility is to re-assign the new values to the same dictionary keys.

var logMessage = new Dictionary<string, string>();
foreach (ReprocessTsk reprocessTsk in reprocessTsks) {
    logMessage["Message"] = "insert into REPROCESS_TSK - parentId changed";
    logMessage["TSKLOC"] = reprocessTsk.TSKLOC;
    logMessage["CRS"] = reprocessTsk.CRS.ToString();
    logMessage["PROCESSED"] = reprocessTsk.PROCESSED.ToString();
    logMessage["OldParentId"] = reprocessTsk.OldParentId;
    logMessage["NewParentId"] = reprocessTsk.NewParentId;

    _logger.LogInformation(JsonConvert.SerializeObject(logMessage));
}

Note that the dictionary indexer creates non existing entries and replaces existing ones. See: the remarks section for the Dictionary<TKey,TValue>.Item[TKey] Property.