Question

I am getting:

“collection was modified enumeration operation may not execute” at this lline:

foreach (Message msg in queue)

after a while.

I have to use .NET 2.0.

The two operations I make on the private List<> named “queue” are as follows:

// 1st function calls this
lock (queue)
{
      queue.Add(msg);
}

// 2nd function calls this
lock (queue)
{
      using (StreamWriter outfile = new StreamWriter("path", true)
      {
             foreach (Message msg in queue) // This is were I get the exception after a while)
             {
                  outfile.WriteLine(JsonConvert.SerializeObject(msg)); 
             }

              queue = new List<Message>();
      }
}

What am I doing wrong?

Answer 1

the parameter which is used by the lick statement should be readonly. See this link

Use readonly private object instead of queqe

Code should be

eadonly object _object = new object();
// 1st function calls this
lock (_object)
{
      queue.Add(msg);
}

// 2nd function calls this
lock (_object)
{
      using (StreamWriter outfile = new StreamWriter("path", true)
      {
             foreach (Message msg in queue) // This is were I get the exception after a while)
             {
                  outfile.WriteLine(JsonConvert.SerializeObject(msg)); 
             }

              queue = new List<Message>();
      }
}