NullReferenceException When Accessing Dictionary Values in C# 10 with Concurrent Access
I'm wondering if anyone has experience with I'm refactoring my project and I've been working on this all day and After trying multiple solutions online, I still can't figure this out..... This might be a silly question, but I'm encountering a `NullReferenceException` when trying to access values from a `ConcurrentDictionary` in a multi-threaded environment. Specifically, I'm using .NET 6 and C# 10. I have the following setup where multiple threads are trying to update and read from the dictionary concurrently: ```csharp using System; using System.Collections.Concurrent; using System.Threading.Tasks; class Program { static ConcurrentDictionary<int, string> myDict = new ConcurrentDictionary<int, string>(); static void Main(string[] args) { // Populate the dictionary for (int i = 0; i < 10; i++) { myDict.TryAdd(i, "Value " + i); } var tasks = new Task[5]; for (int i = 0; i < tasks.Length; i++) { tasks[i] = Task.Run(() => AccessValues()); } Task.WaitAll(tasks); } static void AccessValues() { for (int i = 0; i < 10; i++) { string value = myDict[i]; // This line throws NullReferenceException Console.WriteLine(value); } } } ``` While I expect that accessing a value by key should return the default value for missing keys (in this case, `null`), it seems to throw an exception instead. I've confirmed that the keys I am trying to access do exist in the dictionary, but this issue arises intermittently. I've also tried using `TryGetValue` to avoid the exception and verify if the key exists, like this: ```csharp if(myDict.TryGetValue(i, out string value)) { Console.WriteLine(value); } else { Console.WriteLine("Key not found"); } ``` However, the exception still occurs on the `myDict[i]` line. I need to understand why this is happening and how to safely access dictionary values in a concurrent context. Any insights or suggestions would be greatly appreciated! My development environment is macOS. I'd really appreciate any guidance on this. This is part of a larger API I'm building. Thanks in advance! Thanks, I really appreciate it! I'm developing on Debian with Csharp. For reference, this is a production microservice.