Add memory cache to currency client

RhSolutions.AddIn/Services/CurrencyClient.cs

@@ -1,4 +1,5 @@
-using System.Net;
+using Microsoft.Extensions.Caching.Memory;
+using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
 using System.Xml.Linq;
@@ -8,34 +9,42 @@ namespace RhSolutions.Services;
 public class CurrencyClient : ICurrencyClient
 {
     private readonly HttpClient _httpClient;
+    private readonly IMemoryCache _memoryCache;
     private const string _requestAddress = @"https://www.cbr.ru/scripts/XML_daily.asp?date_req=";
     public HttpStatusCode StatusCode { get; private set; }
 
-    public CurrencyClient(HttpClient httpClient)
+    public CurrencyClient(HttpClient httpClient, IMemoryCache memoryCache)
     {
         _httpClient = httpClient;
+        _memoryCache = memoryCache;
     }
 
     public async Task<decimal?> GetExchangeRate(DateTime date)
     {
-        string request = $"{_requestAddress}{date.Date:dd/MM/yyyy}";
+        if (!_memoryCache.TryGetValue(date, out decimal exchangeRate))
-        HttpResponseMessage response = await _httpClient.GetAsync(request);
-        try
         {
-            response.EnsureSuccessStatusCode();
+            string request = $"{_requestAddress}{date.Date:dd/MM/yyyy}";
-            string xml = await response.Content.ReadAsStringAsync();
+            HttpResponseMessage response = await _httpClient.GetAsync(request);
-            XElement valCourses = XElement.Parse(xml);
+            try
-
+            {
-            decimal? exchangeRate = decimal.Parse(valCourses.Elements("Valute")
+                response.EnsureSuccessStatusCode();
-                .Where(e => e.Element("Name").Value == "Евро")
+                string xml = await response.Content.ReadAsStringAsync();
-                .FirstOrDefault()
+                XElement valCourses = XElement.Parse(xml);
-                .Element("Value").Value);
+                exchangeRate = decimal.Parse(valCourses.Elements("Valute")
-            return exchangeRate;
+                    .Where(e => e.Element("Name").Value == "Евро")
-        }
+                    .FirstOrDefault()
-        catch
+                    .Element("Value").Value);
-        {
+                var cacheEntryOptions = new MemoryCacheEntryOptions()
-            StatusCode = response.StatusCode;
+                    .SetSlidingExpiration(TimeSpan.FromHours(1));
-            return null;
+                _memoryCache.Set(date, exchangeRate, cacheEntryOptions);
+                return exchangeRate;
+            }
+            catch
+            {
+                StatusCode = response.StatusCode;
+                return null;
+            }
         }
+        return exchangeRate;        
     }
 }