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Merge pull request #9 from postsharp/topic/6.7/blazor-sample
Added PostSharp.Samples.Blazor.AutoRetry.
2 parents 6be644c + d7bbda8 commit 4a00d52

30 files changed

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‎Blazor/PostSharp.Samples.Blazor.AutoRetry/App.razor‎

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<Router AppAssembly="@typeof(Program).Assembly">
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<Found Context="routeData">
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<RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
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</Found>
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<NotFound>
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<LayoutView Layout="@typeof(MainLayout)">
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<p>Sorry, there's nothing at this address.</p>
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</LayoutView>
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</NotFound>
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</Router>

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/Aspects/AutoRetryAttribute.cs‎

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using PostSharp.Aspects;
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using PostSharp.Extensibility;
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using PostSharp.Serialization;
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using System;
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using System.Data;
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using System.Linq;
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using System.Net;
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using System.Threading.Tasks;
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namespace PostSharp.Samples.AutoRetry.Aspects
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{
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/// <summary>
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/// Aspect that, when applied to a method, causes invocations of this method to be retried if the method ends with
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/// specified exceptions.
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/// </summary>
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[PSerializable]
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[LinesOfCodeAvoided(5)]
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[MulticastAttributeUsage(MulticastTargets.Method)]
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public sealed class AutoRetryAttribute : MethodInterceptionAspect
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{
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/// <summary>
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/// Initializes a new <see cref="AutoRetryAttribute" /> with default values.
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/// </summary>
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public AutoRetryAttribute()
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{
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// Set the default values for properties.
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MaxRetries = 5;
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Delay = 3;
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HandledExceptions = new[] { typeof(WebException), typeof(DataException) };
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}
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/// <summary>
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/// Gets or sets the maximum number of retries. The default value is 5.
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/// </summary>
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public int MaxRetries
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{
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get; set;
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}
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/// <summary>
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/// Gets or sets the delay before retrying, in seconds. The default value is 3.
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/// </summary>
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public float Delay
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{
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get; set;
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}
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/// <summary>
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/// Gets or sets the type of exceptions that cause the method invocation to be retried. The default value is
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/// <see cref="WebException" /> and <see cref="DataException" />.
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/// </summary>
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public Type[] HandledExceptions
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{
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get; set;
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}
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public override async Task OnInvokeAsync(MethodInterceptionArgs args)
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{
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for (var i = 0; ; i++)
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{
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try
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{
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// Invoke the intercepted method.
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await args.ProceedAsync();
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// If we get here, it means the execution was successful.
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return;
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}
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catch (Exception e)
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{
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// The intercepted method threw an exception. Figure out if we can retry the method.
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if (CanRetry(i, e))
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{
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// Yes, we can retry. Write some message and wait a bit.
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Console.WriteLine(
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$"Method failed with exception {e.GetType().Name} '{e.Message}'. Sleeping {Delay} s and retrying. This was our attempt #{i + 1}.");
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if (Delay > 0)
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{
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await Task.Delay(TimeSpan.FromSeconds(Delay));
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}
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// Continue to the next iteration.
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}
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else
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{
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// No, we cannot retry. Rethrow the exception.
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throw;
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}
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}
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}
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}
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private bool CanRetry(int attempt, Exception e)
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{
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return attempt < MaxRetries &&
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(HandledExceptions == null || HandledExceptions.Any(type => type.IsInstanceOfType(e)));
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}
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}
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}

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/LinkerConfig.xml‎

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<?xml version="1.0" encoding="utf-8" ?>
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<linker>
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<assembly fullname="netstandard">
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<type fullname="*">
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</type>
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</assembly>
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</linker>

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/Pages/FetchData.razor‎

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@page "/fetchdata"
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@inject HttpClient Http
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@using PostSharp.Samples.Blazor.AutoRetry.Services
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<h1>Weather forecast</h1>
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<p>This component demonstrates fetching data from the server with auto-retry on connection failures.</p>
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@if ( forecasts == null )
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{
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<p><em>Loading...</em></p>
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}
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else
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{
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<table class="table">
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<thead>
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<tr>
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<th>Date</th>
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<th>Temp. (C)</th>
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<th>Temp. (F)</th>
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<th>Summary</th>
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</tr>
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</thead>
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<tbody>
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@foreach ( var forecast in forecasts )
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{
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<tr>
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<td>@forecast.Date.ToShortDateString()</td>
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<td>@forecast.TemperatureC</td>
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<td>@forecast.TemperatureF</td>
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<td>@forecast.Summary</td>
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</tr>
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}
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</tbody>
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</table>
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}
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@code {
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private WeatherForecast[] forecasts;
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protected override async Task OnInitializedAsync()
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{
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WeatherService weatherService = new WeatherService( Http );
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forecasts = await weatherService.GetCurrentForecast();
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}
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}

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/Pages/Index.razor‎

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@page "/"
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<h1>Hello, world!</h1>
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Welcome to your new app.
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For more information about Blazor support in PostSharp check out our documentation at <a href="https://doc.postsharp.net/blazor">https://doc.postsharp.net/blazor</a>.

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/PostSharp.Samples.Blazor.AutoRetry.csproj‎

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<Project Sdk="Microsoft.NET.Sdk.Web">
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<PropertyGroup>
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<TargetFramework>netstandard2.1</TargetFramework>
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<RazorLangVersion>3.0</RazorLangVersion>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="3.2.1" />
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<PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Build" Version="3.2.1" PrivateAssets="all" />
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<PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="3.2.1" PrivateAssets="all" />
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<PackageReference Include="PostSharp" Version="6.7.8-preview" />
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<PackageReference Include="System.Net.Http.Json" Version="3.2.0" />
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</ItemGroup>
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<ItemGroup>
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<BlazorLinkerDescriptor Include="LinkerConfig.xml" />
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</ItemGroup>
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</Project>

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/Program.cs‎

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using System;
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using System.Net.Http;
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using System.Collections.Generic;
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using System.Threading.Tasks;
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using System.Text;
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using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
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using Microsoft.Extensions.Configuration;
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using Microsoft.Extensions.DependencyInjection;
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using Microsoft.Extensions.Logging;
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namespace PostSharp.Samples.Blazor.AutoRetry
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{
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public class Program
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{
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public static async Task Main(string[] args)
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{
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var builder = WebAssemblyHostBuilder.CreateDefault(args);
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builder.RootComponents.Add<App>("app");
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builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
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await builder.Build().RunAsync();
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}
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}
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}

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/Properties/launchSettings.json‎

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{
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"iisSettings": {
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"windowsAuthentication": false,
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"anonymousAuthentication": true,
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"iisExpress": {
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"applicationUrl": "http://localhost:1184",
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"sslPort": 0
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}
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},
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"profiles": {
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"IIS Express": {
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"commandName": "IISExpress",
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"launchBrowser": true,
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"inspectUri": "{wsProtocol}://{url.hostname}:{url.port}/_framework/debug/ws-proxy?browser={browserInspectUri}",
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"environmentVariables": {
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"ASPNETCORE_ENVIRONMENT": "Development"
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}
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},
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"PostSharp.Samples.Blazor.AutoRetry": {
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"commandName": "Project",
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"launchBrowser": true,
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"inspectUri": "{wsProtocol}://{url.hostname}:{url.port}/_framework/debug/ws-proxy?browser={browserInspectUri}",
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"applicationUrl": "http://localhost:5000",
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"environmentVariables": {
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"ASPNETCORE_ENVIRONMENT": "Development"
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}
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}
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}
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}

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/README.md‎

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This example demonstrates how to use PostSharp Framework in Blazor WebAssembly applications.
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The application contains one custom `AutoRetry` aspect which is applied to the `WeatherService` class.
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The `AutoRetry` aspect, when applied to a method, retries the execution of the method when the previous execution results in an exception.
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For the purpose of this example the `WeatherService.GetCurrentForecast()` method simulates a connection failure on 50% of all requests.
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The `LinkerConfig.xml` file is required to prevent compatibility issues between the Blazor linker and PostSharp in the Release build.

‎Blazor/PostSharp.Samples.Blazor.AutoRetry/Services/WeatherService.cs‎

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using PostSharp.Samples.AutoRetry.Aspects;
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using System;
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using System.Net;
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using System.Net.Http;
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using System.Net.Http.Json;
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using System.Threading.Tasks;
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namespace PostSharp.Samples.Blazor.AutoRetry.Services
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{
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[AutoRetry]
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public class WeatherService
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{
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private int counter;
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private HttpClient httpClient;
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public WeatherService(HttpClient httpClient)
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{
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this.httpClient = httpClient;
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}
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public async Task<WeatherForecast[]> GetCurrentForecast()
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{
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// Fail every other request.
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if (++counter % 2 == 1)
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{
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throw new WebException("Service unavailable.");
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}
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return await this.httpClient.GetFromJsonAsync<WeatherForecast[]>("sample-data/weather.json");
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}
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}
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public class WeatherForecast
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{
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public DateTime Date
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{
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get; set;
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}
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public int TemperatureC
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{
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get; set;
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}
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public string Summary
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{
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get; set;
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}
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public int TemperatureF => 32 + (int) (TemperatureC / 0.5556);
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}
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}

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