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Showing posts from 2018

Using Redis distributed cache in dotnet core with helper extension methods

Redis cache is out process cache provider for a distributed environment. It is popular in Azure Cloud solution, but it also has a standalone application to operate upon in case of small enterprises application.

How to install Redis Cache on a local machine?
Redis can be used as a local cache server too on our local machines.

At first install, Chocolateyhttps://chocolatey.org/, to make installation of Redis easy. Also, the version under Chocolatey supports more commands and compatible with Official Cache package from Microsoft.
After Chocolatey installation hit choco install redis-64.
Once the installation is done, we can start the server by running redis-server.

Distributed Cache package and registration
dotnet core provides IDistributedCache interface which can be overrided with our own implementation. That is one of the beauties of dotnet core, having DI implementation at heart of framework.

There is already nuget package available to override IDistributedCache i:e Microsoft.Extensio…

Channel, ChannelReader and ChannelWriter to manage data streams in multi-threading environment

I came across Channel class while working with SignalR which looks really interesting. By looking into NuGet packages (https://www.nuget.org/packages/System.Threading.Channels), it seems just 4 months old.

The Channel class provides infrastructure to have multiple reads and write simuletensely through it's Reader and Writer properties.

This is where it is handy in case of SignalR where data streaming needs to be done but is not just limited to that but wherever something needs to be read/write/combination of both in a multi-threading environment.

In my case with SignalR, I had to stream stock data at a regular interval of time.

public ChannelReader<StockData> StreamStock() { var channel = Channel.CreateUnbounded<StockData>(); _stockManager.OnStockData = stockData => { channel.Writer.TryWrite(stockData); }; return channel.Reader; }
The SignalR keeps return type of ChannelReader<StockData> open so that whatever written i…

Blazor 0.5.0 Interop JavaScript from C# and C# to JavaScript call

Blazor provides two-way communication from JS to C# and C# to JS which is called Interop. The version upgrade to Blazor 0.5.0 changed the approach in interactions between cshtml and JS files. The newer version simplifies JS calling by avoiding pre-registration of JS function.

In this article, we would see how to call a JS method by passing multiple parameters from cshtml and parameterized call from JS to cshtml. The scenario that is used in this article has a Kendo AutoComplete to search book and populate information based on the selection.

An example of a call to JS from cshtml

await JSRuntime.Current.InvokeAsync<string>( "searchBook.Init", "#SearchTitle", new DotNetObjectRef(this));
Takeaways from the above example:

- JSRuntime.Current give environment to execute out-process JS.
- InvokeAsync is a function that would allow executing the JS function.
- The searchBook.Init is a JS function call, we would see it in details in the second section.
- Invo…

A wrapper implementation for Kendo Grid usage

A wrapper implementation for any heavily used item is always a good practice. Whatever is not written by us and used at a lot of places should be wrapped within specific functionality to keep it future proof and easily changeable. This also encourages DRY principle to keep our common setting at a central place.

Kendo UI items are enormous in configuration, one of an issue I find people keep repeating codes for Kendo Grid configuration. They have built very flexible system to have any configuration, but in most of the cases, we do not need all of those complicated configuration. We would try to see a simpler configuration of same. The actual core implementation is bit complex, but we do not have to bother about it once done since the focus is just on usage only.

I recommend doing this practice for as simple as jQuery events, form handling or as simple as any notification system. This just won't make things simple but makes codes much more manageable, easy understand, read or open fo…

Making FluentValidation compatible with Swagger including Enum or fixed List support

FluentValidation is not directly compatible with Swagger API to validate models. But they do provide an interface through which we can compose Swagger validation manually. That means we look under FluentValidation validators and compose Swagger validator properties to make it compatible. More of all mapping by reading information from FluentValidation and setting it to Swagger Model Schema.
These can be done on any custom validation from FluentValidation too just that proper schema property has to be available from Swagger.
Custom validation from Enum/List values on FluentValidation using FluentValidation.Validators; using System.Collections.Generic; using System.Linq; using static System.String; /// <summary> /// Validator as per list of items. /// </summary> /// <seealso cref="PropertyValidator" /> public class FixedListValidator : PropertyValidator { /// <summary> /// Gets the valid items /// </sum…

Trim text in MVC Core through Model Binder

Trimming text can be done on client side codes, but I believe it is most suitable on MVC Model Binder since it would be at one place on infrastructure level which would be free from any manual intervention of developer. This would allow every post request to be processed and converted to a trimmed string.

Let us start by creating Model binder

using Microsoft.AspNetCore.Mvc.ModelBinding; using System; using System.Threading.Tasks; public class TrimmingModelBinder : IModelBinder { private readonly IModelBinder FallbackBinder; public TrimmingModelBinder(IModelBinder fallbackBinder) { FallbackBinder = fallbackBinder ?? throw new ArgumentNullException(nameof(fallbackBinder)); } public Task BindModelAsync(ModelBindingContext bindingContext) { if (bindingContext == null) { throw new ArgumentNullException(nameof(bindingContext)); } var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingC…

Custom authorization based on dotnet core policy with Attribute filter

Around 2.5 years back I had written about custom authorization on MVC  Custom authorization on class, action/function, code, area level under Asp.Net MVC application, there are few approaches which are changed in Core version for authorization. Like Authorization filter approach is discouraged since it cannot be unit tested. I believe this is right step but also global or basic authentication could still be driven by Attribute due to enhancing simplicity on codes by focusing on the primary objective rather than writing authorization check everywhere.

The whole approach and usage remain same from the original Post, in this, we would be just looking into making it compatible with dotnet Core MVC. You would need to go through earlier Post to understand the approach that was taken for authorization of a user.

Also, can go through official post: https://docs.microsoft.com/en-us/aspnet/core/security/authorization/policies to understand new approach.

More of all we need to create Requiremen…