Config settings in ASP.NET Core Overview

Config settings in ASP.NET Core Overview

Asp.Net Core Configuration Access configuration settings from appsetting.json in Startup Access configuration settings from custom configuration file in Startup Access config settings from appsetting.json in Controller using DI Access config settings using custom class Access config settings directly from class library

Access config settings directly from class library

In the previous post we saw on how to access the config settings by creating a custom class and injecting it in the startup, so that it can be used in the controllers. In this case the startup and the controller classes are in the same project.

Access config settings using custom class

In the previous post we saw on how to use Dependency Injection to get the configuration options in the Controller classes. In this post we will see another way of reading the configuration setting using a custom class.

Custom Models in Asp.Net Core

So far we have seen CRUD operations using a single table, in real time scenarios we will have to deal with data from multiple tables, like joining multiple tables and returning specific columns from each of the tables. The default Models created using Entity Framework Core will not help in these cases.

For example let us consider the following Employee table, which has references to Department and Country tables.

Entity Framework Core Where clause (Filter rows based on conditions)

To filter a table for specific rows we need to use Where clause and specify a filter condition in the Where clause.

To get all employees who have Age > 30 we need to use the following LINQ Query

Entity Framework Core Select one row from a Table

To select a specific row from a table, we need to use the Select clause and pass the id of the row to be obtained. Let us say we want to get the Employee with EmployeeId = 1 from the employee table then the EF Core query will be as follows.

            var Employee = _context.Employee.Select(e => e.EmployeeId == 1);

Asp.Net Core MVC Model Binding and Validation

Asp.Net Core MVC Model Binding and Validation

Model Binding in ASP.NET Core Model Validation in Asp.Net Core Model Validation Example in Asp.Net Core

Model Validation Example in Asp.Net Core

In the previous post we saw on how to perform form field validations using Model State, in this post we will see an example of using Model Validations in a MVC Form. Following is the Model class with the validations.

Model Validation in Asp.Net Core

Validation is an important part of any application which accepts inputs from users, the data entered by the user needs to be validated for integrity before it is saved in the database. Validations could be on the type of data like int, string, decimal etc. On the format of the data like email, SSN, Phone Number etc. Also we might need custom validation specific to the application.

Asp.Net Core MVC Model validation provides us an easy and effective way to validate user input, using Model validation we can specify the validation parameters in the Model object and the framework will take care of validating the inputs in the View.

Model Binding in ASP.NET Core

Model Binding is the process by which the incoming parameters from a HTTP request are mapped to the parameters of the corresponding Action Methods. The parameters can be route parameters or parameters of the Action methods. Asp.Net core framework takes care of matching the parameters from the request with the route/action method parameters and populated the parameters automatically.

The Framework matched the HTTP parameters with the route/action method parameters using the parameter names, when a parameter name matches it populates the property value from the request and proceeds to match the next parameter.

Asp.Net Core MVC Routing Overview

Asp.Net Core MVC Routing Overview

What is Asp.Net Core MVC Routing Defining multiple routes in Asp.Net Core MVC Attribute routing in Asp.Net Core MVC

Attribute routing in Asp.Net Core MVC

In the previous post we saw about Routing in Asp.Net Core MVC Applications, and how to define Routing in the Applications Startup, this is called conventional routing. Asp.Net Core MVC applications also provide us another way to define routes called Attribute Routing.

Attribute Routing
As the name suggests Attribute Routing is defined by defining routes in action methods using a Route attribute as follows.

Defining multiple routes in Asp.Net Core MVC

In the previous post we saw about Routing in Asp.Net Core MVC Applications, also we saw different ways of defining simple routing. However for more complex application this simple routing might not be enough, we might have to define different routing paths for each module in the application like

/Accounts/. . .
/Contacts/. . .
/Reports/. . .

In this post we shall see on how to define multiple routing paths in Asp.Net Core MVC.

Remember we defined a simple routing which by default was pointing to Home/Index, let us extend this by adding 2 more paths to this routing pointing to the Employee & Users controller, the route definition will be as follows.

What is Asp.Net Core MVC Routing

In traditional Asp.Net Web Forms we access a page using the pages URL like

http://localhost/index.aspx

But in Asp.Net MVC we don’t specify the page name or extension in the URL, instead we specify the Controllers action method in the URL and the controller takes care of rendering the corresponding view. Asp.Net Core MVC uses a routing Middleware to map the incoming request to the action method. Routes can be specified either in the startup or as attributes in the Controller / Action methods.

Injecting Service into Asp.Net Core View

In the previous posts we saw on how register a service Dependency Injection in the startup and inject the service to the MVC controller or Action method. In some cases we might need to inject a service directly into the View. A typical example is populating dropdown lists in the view.

If a view has dropdowns we cannot use the original Entity model since it will not contain the option values for the dropdown lists, in these cases we will create a custom View Model with will contain the properties from the entity model and additional lists to populate the dropdowns in the view. By injecting services to the view directly we can avoid this by injecting services directly to the view to populate the dropdown option values and continue using the entity model to display the model properties.

To inject a service directly to a view we need to use the @Inject directive. The syntax for the @Inject directive is as follows.

Injecting Service into Asp.Net Core Action Methods

In the previous post we saw on how to inject a service to the MVC controller. This might not be needed always, there are cases where we will need the service only for one action method in the controller. In this post we shall see on how to inject a service to one of the action methods in a controller.

The service and the service registration in the startup remains the same, instead of injecting the service in the controller’s constructor. When injecting the service in the action method we need to use the [FromServices] attribute.  We will inject the service in the action method as follows.

Injecting Service into Asp.Net Core Controllers

In the previous example we created an interface IUserService and a service class UserService. We also registered the service in the Asp.Net Core startup. In this post we will see on how to inject this service in the constructor of MVC controller and use it to populate the view. To start with let us create a new MVC controller and name it UserServiceController.

In the constructor of the Controller class we will pass a reference to the IUserService. Since we registered this interface with the service class in the startup, the Asp.Net runtime will inject an instance of the UserService class to the controller. Following is the code for the MVC controller.

ViewModel, Partial Views and Layouts in Asp.Net Core

ViewModel, Partial Views and Layouts in Asp.Net Core

Creating a ViewModel object and bind it to the View Displaying Bootstrap Model in an MVC View Partial views in Asp.Net Core MVC Views Partial view example in Asp.Net Core Partial view with Model example in Asp.Net Core Layout in Asp.Net Core MVC Views

Entity Framework Core with Asp.Net MVC Core Getting Started

Entity Framework Core with Asp.Net MVC Core Getting Started

Setting up Entity Framework Core for MVC Database First Application Creating a controller for CRUD operation using EF Core Creating a List view and display data using EF Core Creating a Detail view and display data using EF Core Creating an Edit view and display data using EF Core Creating a Delete view using EF Core Adding Model Validations in ASP.NET Core MVC Views Customize Validation error message in ASP.NET Core MVC Asp.Net Core MVC - Creating an Empty Controller and develop Manually

Layout in Asp.Net Core MVC Views

Every page on a website will have some common elements like Header, Logo, Menu, Navigation links etc. A layout helps to create a common view for these re-usable part of the page and use it in each page of the application.

A layout is also a view with .cshtml extension. The layout view defines the header, content area and the footer sections. In general re-usable content is placed in the header and footer sections, the content section varying content of the pages. The content section contains a statement @RenderBody(), which embeds the varying content of each page in the content section.

A typical layout view page looks like this.