SignalR now uses System.Text.Json (#14902)

* SignalR now uses System.Text.Json

Starting in 3.0, SignalR no longer defaults to using Newtonsoft.Json

https://docs.microsoft.com/en-us/aspnet/core/migration/22-to-30?view=aspnetcore-3.0&tabs=visual-studio#systemtextjson-is-the-default-protocol

* Address PR feedback

* Documentation -> documentation

* Apply suggestions from code review

Co-Authored-By: Scott Addie <10702007+scottaddie@users.noreply.github.com>

* Update configuration.md (#14958)

* Update configuration.md

* Update configuration.md

aspnetcore/migration/22-to-30.md

@@ -1062,7 +1062,7 @@ In `Startup.ConfigureServices`, call `AddJsonProtocol` to set serializer options
 services.AddSignalR(...)
         .AddJsonProtocol(options =>
         {
-            options.WriteIndented = false;
+            options.PayloadSerializerOptions.WriteIndented = false;
         })
 ```
 
@@ -1073,7 +1073,7 @@ new HubConnectionBuilder()
     .WithUrl("/chatHub")
     .AddJsonProtocol(options =>
     {
-        options.WriteIndented = false;
+        options.PayloadSerializerOptions.WriteIndented = false;
     })
     .Build();
 ```

aspnetcore/signalr/configuration.md

@@ -14,15 +14,16 @@ uid: signalr/configuration
 
 ASP.NET Core SignalR supports two protocols for encoding messages: [JSON](https://www.json.org/) and [MessagePack](https://msgpack.org/index.html). Each protocol has serialization configuration options.
 
-JSON serialization can be configured on the server using the [AddJsonProtocol](/dotnet/api/microsoft.extensions.dependencyinjection.jsonprotocoldependencyinjectionextensions.addjsonprotocol) extension method, which can be added after [AddSignalR](/dotnet/api/microsoft.extensions.dependencyinjection.signalrdependencyinjectionextensions.addsignalr) in your `Startup.ConfigureServices` method. The `AddJsonProtocol` method takes a delegate that receives an `options` object. The [PayloadSerializerSettings](/dotnet/api/microsoft.aspnetcore.signalr.jsonhubprotocoloptions.payloadserializersettings) property on that object is a JSON.NET `JsonSerializerSettings` object that can be used to configure serialization of arguments and return values. See the [JSON.NET Documentation](https://www.newtonsoft.com/json/help/html/Introduction.htm) for more details.
+::: moniker range=">= aspnetcore-3.0"
+
+JSON serialization can be configured on the server using the [AddJsonProtocol](/dotnet/api/microsoft.extensions.dependencyinjection.jsonprotocoldependencyinjectionextensions.addjsonprotocol) extension method. `AddJsonProtocol` can be added after [AddSignalR](/dotnet/api/microsoft.extensions.dependencyinjection.signalrdependencyinjectionextensions.addsignalr) in `Startup.ConfigureServices`. The `AddJsonProtocol` method takes a delegate that receives an `options` object. The [PayloadSerializerOptions](/dotnet/api/microsoft.aspnetcore.signalr.jsonhubprotocoloptions.payloadserializeroptions) property on that object is a `System.Text.Json` <xref:System.Text.Json.JsonSerializerOptions> object that can be used to configure serialization of arguments and return values. For more information, see the [System.Text.Json documentation](/dotnet/api/system.text.json).
 
-As an example, to configure the serializer to use "PascalCase" property names, instead of the default "camelCase" names, use the following code:
+As an example, to configure the serializer to not change the casing of property names, instead of the default "camelCase" names, use the following code in `Startup.ConfigureServices`:
 
 ```csharp
 services.AddSignalR()
     .AddJsonProtocol(options => {
-        options.PayloadSerializerSettings.ContractResolver =
-        new DefaultContractResolver();
+        options.PayloadSerializerOptions.PropertyNamingPolicy = null
     });
 ```
 
@@ -32,6 +33,40 @@ In the .NET client, the same `AddJsonProtocol` extension method exists on [HubCo
 // At the top of the file:
 using Microsoft.Extensions.DependencyInjection;
 
+// When constructing your connection:
+var connection = new HubConnectionBuilder()
+    .AddJsonProtocol(options => {
+        options.PayloadSerializerOptions.PropertyNamingPolicy = null;
+    })
+    .Build();
+```
+
+### Switch to Newtonsoft.Json
+
+If you need features of `Newtonsoft.Json` that aren't supported in `System.Text.Json`, See [Switch to Newtonsoft.Json](xref:migration/22-to-30#switch-to-newtonsoftjson).
+
+::: moniker-end
+
+::: moniker range="<= aspnetcore-2.2"
+
+JSON serialization can be configured on the server using the [AddJsonProtocol](/dotnet/api/microsoft.extensions.dependencyinjection.jsonprotocoldependencyinjectionextensions.addjsonprotocol) extension method, which can be added after [AddSignalR](/dotnet/api/microsoft.extensions.dependencyinjection.signalrdependencyinjectionextensions.addsignalr) in your `Startup.ConfigureServices` method. The `AddJsonProtocol` method takes a delegate that receives an `options` object. The [PayloadSerializerSettings](/dotnet/api/microsoft.aspnetcore.signalr.jsonhubprotocoloptions.payloadserializersettings) property on that object is a JSON.NET `JsonSerializerSettings` object that can be used to configure serialization of arguments and return values. For more information, see the [JSON.NET documentation](https://www.newtonsoft.com/json/help/html/Introduction.htm).
+
+As an example, to configure the serializer to use "PascalCase" property names, instead of the default "camelCase" names, use the following code in `Startup.ConfigureServices`:
+
+```csharp
+services.AddSignalR()
+    .AddJsonProtocol(options => {
+        options.PayloadSerializerSettings.ContractResolver =
+            new DefaultContractResolver();
+    });
+```
+
+In the .NET client, the same `AddJsonProtocol` extension method exists on [HubConnectionBuilder](/dotnet/api/microsoft.aspnetcore.signalr.client.hubconnectionbuilder). The `Microsoft.Extensions.DependencyInjection` namespace must be imported to resolve the extension method:
+
+```csharp
+// At the top of the file:
+using Microsoft.Extensions.DependencyInjection;
+
 // When constructing your connection:
 var connection = new HubConnectionBuilder()
     .AddJsonProtocol(options => {
@@ -41,6 +76,8 @@ var connection = new HubConnectionBuilder()
     .Build();
 ```
 
+::: moniker-end
+
 > [!NOTE]
 > It's not possible to configure JSON serialization in the JavaScript client at this time.