state.sb.Clear() malfunctions sometimes?

[Arad]

I am just getting started with C# , i am experimenting with a socket server , socket server is receiving a string from a client application.

this is the string that is being received by the server :

Value0_Value1_Value2_Value3_Value4_keep5

This is the Code that is receiving the data from client :

    public static void ReadCallback(IAsyncResult ar)
    {
 
        String content = String.Empty;
        StateObject state = (StateObject)ar.AsyncState;
        Socket handler = state.workSocket;
        int bytesRead = handler.EndReceive(ar);
        if (bytesRead > 0)
        {
            state.sb.Clear();
            string proce0, proce1, proce2, proce3, proce4, proce5 = String.Empty;
            state.sb.Append(Encoding.ASCII.GetString(
            state.buffer, 0, bytesRead));
            
            content = state.sb.ToString();
            Console.WriteLine(content);

            string[] Splitdata1 = content.Split('_');
            int splitelements = Splitdata1.Length;
            Console.WriteLine(splitelements);

            if (splitelements == 1)
            {
                proce0 = Splitdata1[0];
                Console.WriteLine("Value: " + proce0);
                state.sb.Clear();

            }
            else if (splitelements == 6)
            {
                proce0 = Splitdata1[0];
                proce1 = Splitdata1[1];
                proce2 = Splitdata1[2];
                proce3 = Splitdata1[3];
                proce4 = Splitdata1[4];
                proce5 = Splitdata1[5];
                Console.WriteLine("Values:\n" + proce0 + "\n" + proce1 + "\n" + proce2 + "\n" + proce3 + "\n" + proce4 + "\n" + proce5 + "\n" + "\n" + "\n");
                state.sb.Clear();
            }
            if (content.IndexOf("END5") > -1)
            {
                Console.WriteLine(content);
                Send(handler, content);
                state.sb.Clear();
            }
            else
            {
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);

            }
        }
    }

Problem i am facing is with the state.sb.clear() , for some reason it doest not always work and sometimes it gives me appended string like this :

Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5Value0_Value1_Value2_Value3_Value4_keep5

instead of just one string like this :

Value0_Value1_Value2_Value3_Value4_keep5

I am attaching the screenshot of the console as well , notice it was working correctly and then it gave the appended string values all of a sudden and then continued normally again .
What could be the cause of this ? is the implementation of state.sb.clear not correct?

 

[Skydiver]

I assume that the sb is state.sb is a StringBuilder. I don't know about later versions of .NET Core, but previous versions of the StringBuilder was not thread safe.

Furthermore, it looks like you are just clobbering the same state.sb by passing around the same state object instead of creating a new one. How do you know one call ReadCallback() is not running concurrently with another call to ReadCallback()?