Address some warnings

Author: nvborisenko

dotnet/src/webdriver/BUILD.bazel

@@ -36,7 +36,7 @@ csharp_library(
     internals_visible_to = [
         "WebDriver.Common.Tests",
     ],
-    langversion = "13.0",
+    langversion = "12.0",
     nullable = "enable",
     resources = [
         "//javascript/atoms/fragments:find-elements.js",
@@ -76,7 +76,7 @@ csharp_library(
     internals_visible_to = [
         "WebDriver.Common.Tests",
     ],
-    langversion = "13.0",
+    langversion = "12.0",
     nullable = "enable",
     resources = [
         "//javascript/atoms/fragments:find-elements.js",
@@ -104,7 +104,7 @@ csharp_library(
     ]) + devtools_version_targets(),
     out = "WebDriver.StrongNamed",
     keyfile = "//dotnet:WebDriver.snk",
-    langversion = "13.0",
+    langversion = "12.0",
     nullable = "enable",
     resources = [
         "//javascript/atoms/fragments:find-elements.js",
@@ -142,7 +142,7 @@ csharp_library(
         "NET8_0_OR_GREATER",
     ],
     keyfile = "//dotnet:WebDriver.snk",
-    langversion = "13.0",
+    langversion = "12.0",
     nullable = "enable",
     resources = [
         "//javascript/atoms/fragments:find-elements.js",

dotnet/src/webdriver/BiDi/Communication/Broker.cs

@@ -375,22 +375,28 @@ private void ProcessReceivedMessage(byte[]? data)
         switch (type)
         {
             case "success":
+                if (id is null) throw new BiDiException("The remote end responded with 'success' message type, but missed required 'id' property.");
+
                 var successCommand = _pendingCommands[id.Value];
-                var messageSuccess = JsonSerializer.Deserialize(ref resultReader, successCommand.Item1.ResultType, _jsonSerializerContext);
+                var messageSuccess = JsonSerializer.Deserialize(ref resultReader, successCommand.Item1.ResultType, _jsonSerializerContext)!;
                 successCommand.Item2.SetResult(messageSuccess);
                 _pendingCommands.TryRemove(id.Value, out _);
                 break;
 
             case "event":
+                if (method is null) throw new BiDiException("The remote end responded with 'event' message type, but missed required 'method' property.");
+
                 var eventType = _eventTypesMap[method];
 
-                var eventArgs = (EventArgs)JsonSerializer.Deserialize(ref paramsReader, eventType, _jsonSerializerContext);
+                var eventArgs = (EventArgs)JsonSerializer.Deserialize(ref paramsReader, eventType, _jsonSerializerContext)!;
 
                 var messageEvent = new MessageEvent(method, eventArgs);
                 _pendingEvents.Add(messageEvent);
                 break;
 
             case "error":
+                if (id is null) throw new BiDiException("The remote end responded with 'error' message type, but missed required 'id' property.");
+
                 var messageError = new MessageError(id.Value) { Error = error, Message = message };
                 var errorCommand = _pendingCommands[messageError.Id];
                 errorCommand.Item2.SetException(new BiDiException($"{messageError.Error}: {messageError.Message}"));

dotnet/src/webdriver/WebDriver.csproj

@@ -4,7 +4,7 @@
     <TargetFrameworks>netstandard2.0;net8.0;</TargetFrameworks>
     <AssemblyName>WebDriver</AssemblyName>
     <RootNamespace>OpenQA.Selenium</RootNamespace>
-    <LangVersion>13.0</LangVersion>
+    <LangVersion>12.0</LangVersion>
     <Nullable>enable</Nullable>
   </PropertyGroup>