Merge pull request #9 from 0xced/Lock-SemaphoreSlim

Fix locking the serviceTable

Author: cerebrate

Arkane.Zeroconf/Providers/Bonjour/ServiceBrowser.cs

@@ -11,6 +11,7 @@
 using System.Collections ;
 using System.Collections.Generic ;
 using System.Diagnostics ;
+using System.Threading ;
 using System.Threading.Tasks ;
 
 #endregion
@@ -30,6 +31,7 @@ public class ServiceBrowser : IServiceBrowser, IDisposable
 
     private readonly Native.DNSServiceBrowseReply            browseReplyHandler ;
     private readonly Dictionary <string, IResolvableService> serviceTable = new() ;
+    private readonly SemaphoreSlim serviceTableSemaphore = new(1, 1) ;
 
     private AddressProtocol address_protocol ;
     private string          domain ;
@@ -54,11 +56,16 @@ public void Browse (uint interfaceIndex, AddressProtocol addressProtocol, string
 
     public IEnumerator <IResolvableService> GetEnumerator ()
     {
-        lock (this)
+        serviceTableSemaphore.Wait();
+        try
         {
             foreach (var service in this.serviceTable.Values)
                 yield return service ;
         }
+        finally
+        {
+            serviceTableSemaphore.Release();
+        }
     }
 
     IEnumerator IEnumerable.GetEnumerator () => this.GetEnumerator () ;
@@ -152,23 +159,29 @@ private void OnBrowseReply (ServiceRef   sdRef,
 
         if ((flags & ServiceFlags.Add) != 0)
         {
-            lock (this.serviceTable)
+            serviceTableSemaphore.Wait();
+            try
+            {
+                this.serviceTable[name] = service;
+            }
+            finally
             {
-                if (this.serviceTable.ContainsKey (name))
-                    this.serviceTable[name] = service ;
-                else
-                    this.serviceTable.Add (name, service) ;
+                serviceTableSemaphore.Release();
             }
 
             var handler = this.ServiceAdded ;
             handler?.Invoke (this, args) ;
         }
         else
         {
-            lock (this.serviceTable)
+            serviceTableSemaphore.Wait();
+            try
+            {
+                this.serviceTable.Remove (name) ;
+            }
+            finally
             {
-                if (this.serviceTable.ContainsKey (name))
-                    this.serviceTable.Remove (name) ;
+                serviceTableSemaphore.Release();
             }
 
             var handler = this.ServiceRemoved ;