Introduce IsOffline

Author: TDroogers

README.md

@@ -74,20 +74,27 @@ example
 ### CachedRequest
 You can give optional settings to the CachedRequest object.
 
-* OneCallPerSession - If true, the result will be returned from sessionstorage if it is not expired. Default: false
-* OneCallPerCache - If true, the result will be returned from localstorage if it is not expired. Default: false
-* IgnoreCache - If true, never return a cached result. Default: false
-* ExpireLocalStorage - The time to expire the result in localstorage. Default: 7 days.
-* ExpireSessionStorage - The time to expire the result in sessionstorage. Default: 15 minutes.
-* CachedAndReplace - If true, The cached result will be returned and the cache will be refreshed for the next call. Default: false
-* RetryOnJsonException - If true, If a JSON exception occurs, the cache will be cleared and the request will be retried. Default: true
+* **OneCallPerSession** - If true, the result will be returned from sessionstorage if it is not expired. *Default: false*
+* **OneCallPerCache** - If true, the result will be returned from localstorage if it is not expired. *Default: false*
+* **IgnoreCache** - If true, never return a cached result. *Default: false*
+* **ExpireLocalStorage** - The time to expire the result in localstorage. *Default: 7 days.*
+* **ExpireSessionStorage** - The time to expire the result in sessionstorage. *Default: 15 minutes.*
+* **CachedAndReplace** - If true, The cached result will be returned and the cache will be refreshed for the next call. *Default: false*
+* **AlwaysCacheWhenOffline** - If true, the cached result will be returned when offline, except when IgnoreCache is true. *Default: false*
+* **RetryOnJsonException** - If true, If a JSON exception occurs, the cache will be cleared and the request will be retried. *Default: true*
 
 ### Global settings
 
 On, for example, MainLayout.razor.cs, you can set the Postfix to be used for all requests. This is useful if you have multiple users using the same app from the same browser.
 
 `ExpireStorageService.Postfix = userId.ToString();`
 
+ExpireStorageService knows two properties to monitor if the app is offline.
+
+IsOffline is true when the last request had an `HttpRequestException`.
+
+`ExpireStorageService.IsOffline` and `ExpireStorageService.IsOfflineChanged`
+
 ### ICacheableResponse
 
 If a response object implements ICacheableResponse, the FromCache property will be set to true if the result was retrieved from cache.

Src/Drogecode.Blazor.ExpireStorage/Drogecode.Blazor.ExpireStorage.csproj

@@ -1,18 +1,28 @@
 <Project Sdk="Microsoft.NET.Sdk.Razor">
 
   <PropertyGroup>
-    <TargetFrameworks>net9.0;net10.0</TargetFrameworks>
+    <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <RootNamespace>Drogecode.Blazor.ExpireStorage</RootNamespace>
-    <Version>0.1.2</Version>
+    <Version>0.2.0</Version>
     <Title>Drogecode.Blazor.ExpireStorage</Title>
     <Authors>Taco Droogers</Authors>
     <PackageProjectUrl>https://github.com/Drogecode/Drogecode.Blazor.ExpireStorage</PackageProjectUrl>
     <RepositoryUrl>https://github.com/Drogecode/Drogecode.Blazor.ExpireStorage</RepositoryUrl>
     <Description>Adds a wrapper on top of Blazored.LocalStorage and Blazored.SessionStorage to expire items from localstorage and sessionstorage after a specified time.</Description>
     <PackageReadmeFile>README.md</PackageReadmeFile>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
+    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+    <NoWarn>$(NoWarn);1591</NoWarn>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
+    <DocumentationFile>bin\Debug\Drogecode.Blazor.ExpireStorage.xml</DocumentationFile>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+    <DocumentationFile>bin\Release\Drogecode.Blazor.ExpireStorage.xml</DocumentationFile>
   </PropertyGroup>
 
   <ItemGroup>
@@ -28,11 +38,6 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-  </ItemGroup>
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net9.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="9.0.10" />
-  </ItemGroup>
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net10.0' ">
     <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="10.0.0" />
   </ItemGroup>
 

Src/Drogecode.Blazor.ExpireStorage/Models/CachedRequest.cs

@@ -31,6 +31,11 @@ public class CachedRequest
     /// Return cached but also call for update
     /// </summary>
     public bool CachedAndReplace { get; set; }
+    
+    /// <summary>
+    /// Always return the cached response when offline, except when IgnoreCache is true.
+    /// </summary>
+    public bool AlwaysCacheWhenOffline { get; set; }
 
     /// <summary>
     /// Retry once on JsonException.

Src/Drogecode.Blazor.ExpireStorage/Services/ExpireStorageService.cs

@@ -1,19 +1,36 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Text.Json;
 using Drogecode.Blazor.ExpireStorage.Helpers;
+using Microsoft.AspNetCore.Components;
 
 namespace Drogecode.Blazor.ExpireStorage;
 
 public class ExpireStorageService : IExpireStorageService
 {
-private readonly ILocalStorageExpireService _localStorageExpireService;
+    private readonly ILocalStorageExpireService _localStorageExpireService;
     private readonly ISessionExpireService _sessionStorageExpireService;
 
     /// <summary>
     /// String to postfix to the key in case multiple users can use the app from the same browser.
     /// </summary>
     public static string? Postfix { get; set; }
 
+    public static EventCallback<bool> IsOfflineChanged { get; set; }
+
+    /// <summary>
+    /// True if the last request failed.
+    /// </summary>
+    public static bool IsOffline
+    {
+        get => field;
+        private set
+        {
+            if (field == value) return;
+            field = value;
+            IsOfflineChanged.InvokeAsync(field);
+        }
+    }
+
     public static bool LogToConsole
     {
         get => ConsoleHelper.LogToConsole;
@@ -29,9 +46,9 @@ public ExpireStorageService(
     }
 
     public async Task<TRes?> CachedRequestAsync<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] TRes>(
-        string cacheKey, 
-        Func<Task<TRes>> function, 
-        CachedRequest? request = null, 
+        string cacheKey,
+        Func<Task<TRes>> function,
+        CachedRequest? request = null,
         CancellationToken clt = default)
     {
         request ??= new CachedRequest();
@@ -41,14 +58,15 @@ public ExpireStorageService(
             {
                 cacheKey += $"__{Postfix}";
             }
+
             if (clt.IsCancellationRequested) return default;
-            if (request.CachedAndReplace)
+            if (request.CachedAndReplace && !(IsOffline && request.AlwaysCacheWhenOffline))
             {
                 var requestCopy = request;
                 _ = Task.Run(async () => await RunSaveAndReturn(cacheKey, function, requestCopy, clt), clt);
             }
 
-            if ((request.CachedAndReplace || request.OneCallPerSession) && !request.IgnoreCache)
+            if ((request.CachedAndReplace || request.OneCallPerSession || (IsOffline && request.AlwaysCacheWhenOffline)) && !request.IgnoreCache)
             {
                 var sessionResult = await _sessionStorageExpireService.GetItemAsync<TRes>(cacheKey, clt);
                 if (sessionResult is not null)
@@ -57,11 +75,12 @@ public ExpireStorageService(
                     {
                         response.FromCache = true;
                     }
+
                     return sessionResult;
                 }
             }
 
-            if ((request.CachedAndReplace || request.OneCallPerCache) && !request.IgnoreCache)
+            if ((request.CachedAndReplace || request.OneCallPerCache || (IsOffline && request.AlwaysCacheWhenOffline)) && !request.IgnoreCache)
             {
                 var cacheResult = await _localStorageExpireService.GetItemAsync<TRes?>(cacheKey, clt);
                 if (cacheResult is not null)
@@ -70,6 +89,7 @@ public ExpireStorageService(
                     {
                         response.FromCache = true;
                     }
+
                     return cacheResult;
                 }
             }
@@ -82,6 +102,7 @@ public ExpireStorageService(
         catch (HttpRequestException)
         {
             ConsoleHelper.WriteLine("a HttpRequestException");
+            IsOffline = true;
         }
         catch (TaskCanceledException)
         {
@@ -110,6 +131,7 @@ public ExpireStorageService(
         catch (HttpRequestException)
         {
             ConsoleHelper.WriteLine("b HttpRequestException");
+            IsOffline = true;
         }
         catch (TaskCanceledException)
         {
@@ -119,7 +141,6 @@ public ExpireStorageService(
             // The object definition could be changed with an update. Deleting the old version and retrying again to get the latest version.
             ConsoleHelper.WriteLine($"JsonException for {cacheKey}, Deleting");
             await _localStorageExpireService.DeleteItemAsync(cacheKey, clt);
-            request ??= new CachedRequest();
             if (request.RetryOnJsonException) // Only retry once
             {
                 ConsoleHelper.WriteLine($"Retry calling {cacheKey}");
@@ -143,6 +164,7 @@ private async Task<TRes> RunSaveAndReturn<TRes>(string cacheKey, Func<Task<TRes>
         await _localStorageExpireService.SetItemAsync(cacheKey, result, request.ExpireLocalStorage, clt);
         if (request.OneCallPerSession)
             await _sessionStorageExpireService.SetItemAsync(cacheKey, result, request.ExpireSession, clt);
+        IsOffline = false;
         return result;
     }
 }