Modified S5144(C#): Use HttpClient instead of old WebRequest (#4431)

rules/S5144/csharp/how-to-fix-it/dotnet.adoc

@@ -14,11 +14,14 @@ using System.Web.Mvc;
 public class ExampleController: Controller
 {
     [HttpGet]
-    public IActionResult ImageFetch(string location)
+    public async Task<IActionResult> ImageFetch(string location)
     {
-        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(location);
+        await using Stream stream =
+            await client.GetStreamAsync(location); // Noncompliant
+        var exampleImage =
+            await JsonSerializer.DeserializeAsync<ExampleImage>(stream);
 
-        return Ok();
+        return Ok(example ?? new());
     }
 }
 ----
@@ -36,7 +39,7 @@ public class ExampleController: Controller
     private readonly string[] allowedDomains = { "trusted1.example.com", "trusted2.example.com" };
 
     [HttpGet]
-    public IActionResult ImageFetch(string location)
+    public async Task<IActionResult> ImageFetch(string location)
     {
         Uri uri = new Uri(location);
 
@@ -45,9 +48,12 @@ public class ExampleController: Controller
             return BadRequest();
         }
 
-        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
+        await using Stream stream =
+            await client.GetStreamAsync(location);
+        var exampleImage =
+            await JsonSerializer.DeserializeAsync<ExampleImage>(stream);
 
-        return Ok();
+        return Ok(example ?? new());
     }
 }
 ----