Merge pull request #237310 from TimothyMothra/patch-1

Update opentelemetry-enable.md - cleaning up .NET examples

Author: v-regandowner

articles/azure-monitor/app/opentelemetry-configuration.md

@@ -20,7 +20,42 @@ A connection string in Application Insights defines the target location for send
 
 ### [.NET](#tab/net)
 
-Currently unavailable.
+Use one of the following three ways to configure the connection string:
+
+- Add `UseAzureMonitor()` to your application startup. Depending on your version of .NET, this will be in either your `startup.cs` or `program.cs` class.
+    ```csharp
+    using Azure.Monitor.OpenTelemetry.AspNetCore;
+    using Microsoft.AspNetCore.Builder;
+    using Microsoft.Extensions.DependencyInjection;
+
+    var builder = WebApplication.CreateBuilder(args);
+
+    builder.Services.AddOpenTelemetry().UseAzureMonitor(options => {
+        options.ConnectionString = "<Your Connection String>";
+    });
+
+    var app = builder.Build();
+
+    app.Run();
+    ```
+- Set an environment variable:
+   ```console
+   APPLICATIONINSIGHTS_CONNECTION_STRING=<Your Connection String>
+   ```
+- Add the following section to your `appsettings.json` config file:
+  ```json
+  {
+    "AzureMonitor": {
+        "ConnectionString": "<Your Connection String>"
+    }
+  }
+  ```
+  
+> [!NOTE]
+> If you set the connection string in more than one place, we adhere to the following precedence:
+> 1. Code
+> 2. Environment Variable
+> 3. Configuration File
 
 ### [Java](#tab/java)
 
@@ -187,9 +222,26 @@ export OTEL_TRACES_SAMPLER_ARG=0.1
 You might want to enable Azure Active Directory (Azure AD) Authentication for a more secure connection to Azure, which prevents unauthorized telemetry from being ingested into your subscription.
 
 #### [.NET](#tab/net)
-    
+
+We support the credential classes provided by [Azure Identity](https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/identity/Azure.Identity#credential-classes).
+
+- We recommend `DefaultAzureCredential` for local development.
+- We recommend `ManagedIdentityCredential` for system-assigned and user-assigned managed identities.
+  - For system-assigned, use the default constructor without parameters.
+  - For user-assigned, provide the client ID to the constructor.
+- We recommend `ClientSecretCredential` for service principals.
+  - Provide the tenant ID, client ID, and client secret to the constructor.
+
 ```csharp
-Currently unavailable.
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddOpenTelemetry().UseAzureMonitor(options => {
+    options.Credential = new DefaultAzureCredential();
+});
+
+var app = builder.Build();
+
+app.Run();
 ```
 
 #### [Java](#tab/java)
@@ -396,7 +448,12 @@ The following OpenTelemetry configurations can be accessed through environment v
 
 ### [.NET](#tab/net)
 
-Currently unavailable.
+| Environment variable       | Description                                        |
+| -------------------------- | -------------------------------------------------- |
+| `APPLICATIONINSIGHTS_CONNECTION_STRING` | Set this to the connection string for your Application Insights resource. |
+| `APPLICATIONINSIGHTS_STATSBEAT_DISABLED` | Set this to `true` to opt-out of internal metrics collection. |
+| `OTEL_RESOURCE_ATTRIBUTES` | Key-value pairs to be used as resource attributes. See the [Resource SDK specification](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.5.0/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable) for more details. |
+| `OTEL_SERVICE_NAME`        | Sets the value of the `service.name` resource attribute. If `service.name` is also provided in `OTEL_RESOURCE_ATTRIBUTES`, then `OTEL_SERVICE_NAME` takes precedence. |
 
 ### [Java](#tab/java)
 

articles/azure-monitor/app/opentelemetry-enable.md

@@ -136,12 +136,7 @@ using Microsoft.Extensions.DependencyInjection;
 
 var builder = WebApplication.CreateBuilder(args);
 
-builder.Services.AddOpenTelemetry().UseAzureMonitor(
-
-//Uncomment the line below when setting the Application Insights Connection String via code
-//options => options.ConnectionString = "<Your Connection String>"
-
-);
+builder.Services.AddOpenTelemetry().UseAzureMonitor();
 
 var app = builder.Build();
 
@@ -487,7 +482,7 @@ The following table represents the currently supported custom telemetry types:
 | Language                                  | Custom Events | Custom Metrics | Dependencies | Exceptions | Page Views | Requests | Traces |
 |-------------------------------------------|---------------|----------------|--------------|------------|------------|----------|--------|
 | **ASP.NET Core**                          |               |                |              |            |            |          |        |
-| &nbsp;&nbsp;&nbsp;OpenTelemetry API       |               |                | Yes          | Yes        |            | Yes      |        |
+| &nbsp;&nbsp;&nbsp;OpenTelemetry API       |               | Yes            | Yes          | Yes        |            | Yes      |        |
 | &nbsp;&nbsp;&nbsp;iLogger API             |               |                |              |            |            |          | Yes    |
 | &nbsp;&nbsp;&nbsp;AI Classic API          |               |                |              |            |            |          |        |
 |                                           |               |                |              |            |            |          |        |
@@ -750,45 +745,6 @@ private static IEnumerable<Measurement<int>> GetThreadState(Process process)
 }
 ```
 
-
-```csharp
-using System.Diagnostics.Metrics;
-using Azure.Monitor.OpenTelemetry.Exporter;
-using OpenTelemetry;
-using OpenTelemetry.Metrics;
-
-public class Program
-{
-    internal static readonly Meter meter = new("OTel.AzureMonitor.Demo");
-
-    public static void Main()
-    {
-        using var meterProvider = Sdk.CreateMeterProviderBuilder()
-            .AddMeter("OTel.AzureMonitor.Demo")
-            .AddAzureMonitorMetricExporter(o =>
-            {
-                o.ConnectionString = "<Your Connection String>";
-            })
-            .Build();
-
-        var process = Process.GetCurrentProcess();
-        
-        ObservableGauge<int> myObservableGauge = meter.CreateObservableGauge("Thread.State", () => GetThreadState(process));
-
-        System.Console.WriteLine("Press Enter key to exit.");
-        System.Console.ReadLine();
-    }
-    
-    private static IEnumerable<Measurement<int>> GetThreadState(Process process)
-    {
-        foreach (ProcessThread thread in process.Threads)
-        {
-            yield return new((int)thread.ThreadState, new("ProcessId", process.Id), new("ThreadId", thread.Id));
-        }
-    }
-}
-```
-
 #### [Java](#tab/java)
 
 ```Java
@@ -1314,11 +1270,11 @@ To add span attributes, use either of the following two ways:
 * Add a custom span processor.
 
 > [!TIP]
-> The advantage of using options provided by instrumentation libraries, when they're available, is that the entire context is available. As a result, users can select to add or filter more attributes. For example, the enrich option in the HttpClient instrumentation library gives users access to the httpRequestMessage itself. They can select anything from it and store it as an attribute.
+> The advantage of using options provided by instrumentation libraries, when they're available, is that the entire context is available. As a result, users can select to add or filter more attributes. For example, the enrich option in the HttpClient instrumentation library gives users access to the [HttpRequestMessage](/dotnet/api/system.net.http.httprequestmessage) and the [HttpResponseMessage](/dotnet/api/system.net.http.httpresponsemessage) itself. They can select anything from it and store it as an attribute.
 
 1. Many instrumentation libraries provide an enrich option. For guidance, see the readme files of individual instrumentation libraries:
     - [ASP.NET Core](https://github.com/open-telemetry/opentelemetry-dotnet/blob/1.0.0-rc9.14/src/OpenTelemetry.Instrumentation.AspNetCore/README.md#enrich)
-    - [HttpClient and HttpWebRequest](https://github.com/open-telemetry/opentelemetry-dotnet/blob/1.0.0-rc9.14/src/OpenTelemetry.Instrumentation.Http/README.md#enrich)
+    - [HttpClient](https://github.com/open-telemetry/opentelemetry-dotnet/blob/1.0.0-rc9.14/src/OpenTelemetry.Instrumentation.Http/README.md#enrich)
 
 1. Use a custom processor: