Add ResponseFormatMiddleware

Api/Api.csproj

@@ -13,6 +13,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.4.0" />
   </ItemGroup>
 

Api/Middleware/ResponseFormatMiddleware.cs

+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using System.Xml;
+
+public class ResponseFormatMiddleware
+{
+    private readonly RequestDelegate _next;
+
+    public ResponseFormatMiddleware(RequestDelegate next) => _next = next;
+
+    public async Task InvokeAsync(HttpContext context)
+    {
+        var originalBodyStream = context.Response.Body;
+        using var responseBody = new MemoryStream();
+        context.Response.Body = responseBody;
+
+        await _next(context);
+
+        context.Response.Body.Seek(0, SeekOrigin.Begin);
+        var responseText = await new StreamReader(context.Response.Body).ReadToEndAsync();
+
+        context.Response.Body.Seek(0, SeekOrigin.Begin);
+        context.Response.Body = originalBodyStream;
+
+        if (context.Request.Query.TryGetValue("format", out var formatValue) && formatValue.ToString().Equals("xml", StringComparison.OrdinalIgnoreCase))
+        {
+            context.Response.ContentType = "application/xml";
+            await context.Response.WriteAsync(ConvertJsonToXml(responseText));
+        }
+        else
+        {
+            context.Response.ContentType = "application/json";
+            await context.Response.WriteAsync(responseText);
+        }
+    }
+
+    private string ConvertJsonToXml(string json)
+    {
+        try
+        {
+            JToken parsedJson = JToken.Parse(json);
+            if (parsedJson is JArray) json = $"{{\"Root\": {json}}}";
+
+            var doc = JsonConvert.DeserializeXmlNode(json, "Root");
+            if (doc == null) return "<error>Unable to convert JSON to XML; null document</error>";
+
+            using var stringWriter = new StringWriter();
+            using var xmlTextWriter = new XmlTextWriter(stringWriter);
+            doc.WriteTo(xmlTextWriter);
+            return stringWriter.ToString();
+        }
+        catch
+        {
+            return "<error>Unable to convert JSON to XML</error>";
+        }
+    }
+}

Api/Program.cs

@@ -102,8 +102,8 @@ app.UseHttpsRedirection();
 app.UseAuthorization();
 
 app.UseMiddleware<AuthenticationMiddleware>();
-
 app.UseMiddleware<RequestLoggingMiddleware>();
+app.UseMiddleware<ResponseFormatMiddleware>();
 
 app.MapControllers();