Tag: .NET

Data Binding in ASP.NET Core Blazor

- by mahmood 
<p>
    <input @bind="inputValue" />
</p>

<p>@inputValue</p>

@code {
    private string? inputValue;
}

Equivalent HTML binding

<p>
    <label>
        Normal Blazor binding: 
        <input @bind="InputValue" />
    </label>
</p>

<p>
    <label>
        Demonstration of equivalent HTML binding: 
        <input value="@InputValue"
            @onchange="@((ChangeEventArgs __e) => InputValue = __e?.Value?.ToString())" />
    </label>
</p>

<p>
    <code>InputValue</code>: @InputValue
</p>

@code {
    private string? InputValue { get; set; }
}

Bind a property or field on other Document Object Model (DOM) events

@page "/bind-event"

<p>
    <input @bind="InputValue" @bind:event="oninput" />
</p>

<p>
    <code>InputValue</code>: @InputValue
</p>

@code {
    private string? InputValue { get; set; }
}

References
https://docs.microsoft.com/en-us/aspnet/core/blazor/components/data-binding

Transient fault handling in gRPC with retries in C#

- by mahmood

gRPC calls can be interrupted by transient faults. Transient faults include:

  • Momentary loss of network connectivity.
  • Temporary unavailability of a service.
  • Timeouts due to server load.

When a gRPC call is interrupted, the client throws an RpcException with details about the error. The client app must catch the exception and choose how to handle the error.

var client = new Greeter.GreeterClient(channel);
try
{
    var response = await client.SayHelloAsync(
        new HelloRequest { Name = ".NET" });

    Console.WriteLine("From server: " + response.Message);
}
catch (RpcException ex)
{
    // Write logic to inspect the error and retry
    // if the error is from a transient fault.
}

Duplicating retry logic throughout an app is verbose and error-prone. Fortunately, the .NET gRPC client now has built-in support for automatic retries. Retries are centrally configured on a channel, and there are many options for customizing retry behavior using a RetryPolicy.

var defaultMethodConfig = new MethodConfig
{
    Names = { MethodName.Default },
    RetryPolicy = new RetryPolicy
    {
        MaxAttempts = 5,
        InitialBackoff = TimeSpan.FromSeconds(1),
        MaxBackoff = TimeSpan.FromSeconds(5),
        BackoffMultiplier = 1.5,
        RetryableStatusCodes = { StatusCode.Unavailable }
    }
};

// Clients created with this channel will automatically retry failed calls.
var channel = GrpcChannel.ForAddress("https://localhost:5001", new GrpcChannelOptions
{
    ServiceConfig = new ServiceConfig { MethodConfigs = { defaultMethodConfig } }
});

References
https://devblogs.microsoft.com/dotnet/grpc-in-dotnet-6/
https://docs.microsoft.com/en-us/aspnet/core/grpc/retries?view=aspnetcore-6.0

gRPC client-side load balancing in C#

- by mahmood

The following code example configures a channel to use DNS service discovery with round-robin load balancing:

var channel = GrpcChannel.ForAddress(
    "dns:///my-example-host",
    new GrpcChannelOptions
    {
        Credentials = ChannelCredentials.Insecure,
        ServiceConfig = new ServiceConfig { LoadBalancingConfigs = { new RoundRobinConfig() } }
    });
var client = new Greet.GreeterClient(channel);

var response = await client.SayHelloAsync(new HelloRequest { Name = "world" });

References
https://devblogs.microsoft.com/dotnet/grpc-in-dotnet-6/
https://docs.microsoft.com/en-us/aspnet/core/grpc/loadbalancing?view=aspnetcore-6.0

Parallel.ForEachAsync in .NET 6

- by mahmood 
using System.Net.Http.Headers;
using System.Net.Http.Json;

var userHandlers = new []  { "users/VahidN", "users/shanselman", "users/jaredpar", "users/davidfowl" };

using HttpClient client = new()
{
    BaseAddress = new Uri("https://api.github.com"),
};
client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("DotNet", "6"));

ParallelOptions parallelOptions = new() { MaxDegreeOfParallelism = 3 };

await Parallel.ForEachAsync(userHandlers, parallelOptions, async (uri, token) =>
{
    var user = await client.GetFromJsonAsync<GitHubUser>(uri, token);
    Console.WriteLine($"Name: {user.Name}\nBio: {user.Bio}\n");
});

public class GitHubUser
{
    public string Name { get; set; }
    public string  Bio { get; set; }
}

References
https://www.hanselman.com/blog/parallelforeachasync-in-net-6

Dependency Injection in WPF Application using Generic HostBuilder

- by mahmood

Creating Generic HostBuilder

Nuget :

PM> Install-Package Microsoft.Extensions.Hosting -Version 3.1.2

The HostBuilder class is available from the following namespace,

using Microsoft.Extensions.Hosting;

Initialize the Host

Within Constructor of App class(file: App.xaml.cs) please add below code to build Host,

host = new HostBuilder()
           .ConfigureServices((hostContext, services) =>
           {
 
           }).Build();

DI Container

host = new HostBuilder()
          .ConfigureServices((hostContext, services) =>
          {
              //Add business services as needed
              services.AddScoped<IEmployeeViewModel, EmployeeViewModel>();
 
              //Lets Create single tone instance of Master windows
              services.AddSingleton<EmployeeWindow>();
 
          }).Build();

Setting up OnStartup and OnExit Application events

private void OnStartup(object sender, StartupEventArgs e)
        {
            var mainWindow = host.Services.GetService<EmployeeWindow>();
            mainWindow.Show();
        }
protected override async void OnExit(ExitEventArgs e)
       {
           using (host)
           {
               await host.StopAsync();
           }
 
           base.OnExit(e);
       }

App.XAML file used as below,

<Application x:Class="WPFDesktopApp.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            Startup="OnStartup">
    <Application.Resources>
         
    </Application.Resources>
</Application>

References
https://www.thecodebuzz.com/dependency-injection-wpf-generic-hostbuilder-net-core/
https://laurentkempe.com/2019/09/03/WPF-and-dotnet-Generic-Host-with-dotnet-Core-3-0/

Serialize objects in file with protobuf in C#

- by mahmood 
Install-Package protobuf-net

Decorate your classes

[ProtoContract]
class Person {
    [ProtoMember(1)]
    public int Id {get;set;}
    [ProtoMember(2)]
    public string Name {get;set;}
    [ProtoMember(3)]
    public Address Address {get;set;}
}
[ProtoContract]
class Address {
    [ProtoMember(1)]
    public string Line1 {get;set;}
    [ProtoMember(2)]
    public string Line2 {get;set;}
}

Serialize your data

var person = new Person {
    Id = 12345, Name = "Fred",
    Address = new Address {
        Line1 = "Flat 1",
        Line2 = "The Meadows"
    }
};
using(var file = new FileStream(path, FileMode.Truncate)) {
    Serializer.Serialize(file, person);
    file.SetLength(file.Position);
}
if (!File.Exists(Statics.UserProtobufFile))
{
    using (var file = new FileStream(Statics.UserProtobufFile, FileMode.Create))
    {
        Serializer.Serialize(file, Statics.User);
        file.SetLength(file.Position);
    }
}
else
{
    using (var file = new FileStream(Statics.UserProtobufFile, FileMode.Truncate))
    {
        Serializer.Serialize(file, Statics.User);
        file.SetLength(file.Position);
    }
}

Deserialize your data

Person newPerson;
using (var file = File.OpenRead("person.bin")) {
    newPerson = Serializer.Deserialize<Person>(file);
}

References
https://github.com/protobuf-net/protobuf-net
https://stackoverflow.com/questions/20369302/how-to-serialize-several-objects-in-one-file-in-c-sharp-with-protobuf
https://stackoverflow.com/questions/2152978/using-protobuf-net-i-suddenly-got-an-exception-about-an-unknown-wire-type