Explain how to configure a proxy server via code

.openpublishing.redirection.azure.json

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+        },
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docs/azure/sdk/configure-proxy.md

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+---
+title: Configure a proxy server when using the Azure SDK for .NET 
+description: Learn different ways to configure a proxy server for use with the Azure SDK for .NET client libraries.
+ms.topic: conceptual
+ms.custom: devx-track-dotnet, engagement-fy23
+ms.date: 11/15/2024
+---
+
+# Configure a proxy server when using the Azure SDK for .NET
+
+If your organization requires the use of a proxy server to access Internet resources, some configuration is required to use the Azure SDK for .NET client libraries. Once configured, the proxy is applied to the `HttpClient` instance used for HTTP operations.
+
+## Configure using code
+
+To programmatically configure a proxy for use in underlying HTTP operations supporting the Azure SDK for .NET libraries, complete the following steps:
+
+1. Create an <xref:System.Net.Http.HttpClientHandler> object whose `Proxy` property is set.
+1. Create a service client options object whose <xref:Azure.Core.ClientOptions.Transport%2A> property is set to an `HttpClientTransport` object accepting the `HttpClientHandler` instance.
+1. Pass the service client options object to the service client constructor.
+
+Using the Azure Key Vault Secrets library as an example, you'd have the following code:
+
+:::code language="csharp" source="snippets/configure-proxy/Program.cs":::
+
+## Configure using environment variables
+
+Depending on if your proxy server uses HTTP or HTTPS, you'll set either the environment variable `HTTP_PROXY` or `HTTPS_PROXY`, respectively. The proxy server URL takes the form `http[s]://[username:password@]<ip_address_or_hostname>:<port>/`, where the `username:password` combination is optional. To get the IP address or hostname, port, and credentials for your proxy server, consult your network administrator.
+
+The following examples show how to set the appropriate environment variables in command shell (Windows) and bash (Linux/macOS) environments. Setting the appropriate environment variable causes the Azure SDK for .NET libraries to use the proxy server at runtime.
+
+### [cmd](#tab/cmd)
+
+```cmd
+rem Non-authenticated HTTP server:
+set HTTP_PROXY=http://10.10.1.10:1180
+
+rem Authenticated HTTP server:
+set HTTP_PROXY=http://username:[email protected]:1180
+
+rem Non-authenticated HTTPS server:
+set HTTPS_PROXY=http://10.10.1.10:1180
+
+rem Authenticated HTTPS server:
+set HTTPS_PROXY=http://username:[email protected]:1180
+```
+
+### [bash](#tab/bash)
+
+```bash
+# Non-authenticated HTTP server:
+HTTP_PROXY=http://10.10.1.10:1180
+
+# Authenticated HTTP server:
+HTTP_PROXY=http://username:[email protected]:1180
+
+# Non-authenticated HTTPS server:
+HTTPS_PROXY=http://10.10.1.10:1180
+
+# Authenticated HTTPS server:
+HTTPS_PROXY=http://username:[email protected]:1180
+```
+
+---

docs/azure/sdk/snippets/configure-proxy/Program.cs

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+using System.Net;
+using Azure.Core.Pipeline;
+using Azure.Identity;
+using Azure.Security.KeyVault.Secrets;
+
+using HttpClientHandler handler = new()
+{
+    Proxy = new WebProxy(new Uri("<http://example.com>")),
+};
+
+SecretClientOptions options = new()
+{
+    Transport = new HttpClientTransport(handler),
+};
+SecretClient client = new(
+    new Uri("https://<key-vault-name>.vault.azure.net/"),
+    new DefaultAzureCredential(),
+    options);

docs/azure/sdk/snippets/configure-proxy/ProxyServerConfiguration.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Identity" Version="1.13.1" />
+    <PackageReference Include="Azure.Security.KeyVault.Secrets" Version="4.7.0" />
+  </ItemGroup>
+
+</Project>