DotNetCore-MVC-SQL-Angular-Html: May 2022

.Net Core applications contains appsettings.json, it contains major configurations related to application, Environment, Database, etc.

Some config key values will be different depends on the environment, example Development, Staging, Production. In this scenario we need maintain key values depends on environment.

Let see how to overcome this issue, Example DB configuration will be different for every environment so we need maintain different appsettings.<Environment>.json file like child of appsettings.json.

Based on Environment flag it will override the values i,e take vales from appsettings.<Environment>.json override in appsettings.json at runtime.

1.Set Environment Variable

Properties folder -> launchSettings.json file we can set environment values.

Example Set it as Development

{
    "$schema": "https://json.schemastore.org/launchsettings.json",
    "iisSettings": {
      "windowsAuthentication": false,
      "anonymousAuthentication": true,
      "iisExpress": {
        "applicationUrl": "http://localhost:8320",
        "sslPort": 44311
      }
    },
    "profiles": {
      "SolidPrinciples": {
        "commandName": "Project",
        "dotnetRunMessages": true,
        "launchBrowser": true,
        "launchUrl": "swagger",
        "applicationUrl": "https://localhost:7033;http://localhost:5033",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Development"
        }
      },
      "IIS Express": {
        "commandName": "IISExpress",
        "launchBrowser": true,
        "launchUrl": "swagger",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Development"
        }
      }
    }
  }
  

appsetings.json

{
    "Logging": {
      "LogLevel": {
        "Default": "Information",
        "Microsoft.AspNetCore": "Warning"
      }
    },
    "AllowedHosts": "*",
    "Environment": "Prod",
    "ConnectionStrings": {
      ///we need to alter corresponding actual DB connection string.
      "DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=Prod;"
    }
  }
  

appsetings.Development.json

{
    "Environment": "Development",
    "ConnectionStrings": {
      ///we need to alter corresponding actual DB connection string.
      "DefaultConnection": "Server=(Development)\\MSSQLLocalDB;Database=Development;"
    }
  }
  

appsetings.Staging.json

{
    "Environment": "Staging",
    "ConnectionStrings": {
      ///we need to alter corresponding actual DB connection string.
      "DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=Staging;"
    }
 }
  

In API code we try to consume Environment key from appsetings.

    [Route("api/[controller]")]

    [ApiController]

    public class AppRegionController : ControllerBase

{

        private readonly ILogger<WeatherForecastController> _logger;

        private readonly IConfiguration _configuration;

        public AppRegionController(ILogger<WeatherForecastController> logger, IConfiguration configuration)

{

            _logger = logger;

            _configuration = configuration;

}

        [HttpGet(Name = "ApplicationRegion")]

        public string Get()

{

/// it will return value is Development from appsetings.development.json

            var env = _configuration["Environment"];

            var db= _configuration["ConnectionStrings:DefaultConnection"];

            return env;

}

}

Now run application and read through api call ,values we will get like below.

Request URL

https://localhost:7033/api/AppRegion

Server response

Code	Details
200	Response body Download `Development` Response headers content-type: text/plain; charset=utf-8 date: Tue,24 May 2022 10:43:52 GMT server: Kestrel

Now change environment to staging like below

{
    "$schema": "https://json.schemastore.org/launchsettings.json",
    "iisSettings": {
      "windowsAuthentication": false,
      "anonymousAuthentication": true,
      "iisExpress": {
        "applicationUrl": "http://localhost:8320",
        "sslPort": 44311
      }
    },
    "profiles": {
      "SolidPrinciples": {
        "commandName": "Project",
        "dotnetRunMessages": true,
        "launchBrowser": true,
        "launchUrl": "swagger",
        "applicationUrl": "https://localhost:7033;http://localhost:5033",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Staging"
        }
      },
      "IIS Express": {
        "commandName": "IISExpress",
        "launchBrowser": true,
        "launchUrl": "swagger",
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Staging"
        }
      }
    }
  }

Call same API we will get Staging as response.

Request URL

https://localhost:7033/api/AppRegion

Server response

Code	Details
200	Response body Download `Staging`

Note:

In case keys not exist in region config but Exist in appsetings.json then it will take it from appsetings.json

Both files exist same then it will override based on environment.

When we deploy all appsettings file exist in build folder.

Environment Based We can enable/Disable feature

Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
if(app.Environment.IsStaging())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

SOLID principles provide us with ways to move from tightly coupled code and little encapsulation to the desired results of loosely coupled and encapsulated real needs of a business properly.

SOLID expansion below

S: Single Responsibility Principle (SRP)

O: Open closed Principle (OCP)

L: Liskov substitution Principle (LSP)

I: Interface Segregation Principle (ISP)

D: Dependency Inversion Principle (DIP)

Single Responsibility Principle (SRP):

SRP suggest only one prime functionality exist in single class & functions.

Single class should not include multiple functions and properties which is not related or common reusable.

This means that every class, or similar structure, in your code should have only one job to do.

Everything in that class should be related to a single purpose.

Example :

Phone number validation, Email validation.

Sometimes we will include these validations within same class like User.class itself but SRP suggest we need to split and create separate class like EmailValidation.class & PhoneNoValidation.class

public class User
{
        public Guid Id { get; set; }

        public string Name { get; set; }
        
        public string Email { get; set; }

        ///Not In SRP
        //public static bool IsValidEmail(string email)
        //{
        //    if (email == null || !email.Contains("@"))
        //    {
        //        return false;
        //    }
        //    return true;
        //}

   }

above class IsValidEmail function is not related user it can be use any email validation so need to create separate one.

public class EmailValidationService
    {
        public static bool IsValidEmail(string email)
        {
            /// sample validation just for understanding SRP
            if (email == null || !email.Contains("@"))
            {
                return false;
            }
            return true;
        }
    } 

O: Open/Closed Principle

The Open/closed Principle says "A software module/class is open for extension and closed for modification".

Here "Open for extension" means, we need to design our module/class in such a way that the new functionality can be added only when new requirements are generated. "Closed for modification" means we have already developed a class and it has gone through unit testing. We should then not alter it until we find bugs. As it says, a class should be open for extensions, we can use inheritance to do this

Best Example ;

1. we need to find interest calculation but each and every bank have their own calculations but outcome result is interest so should not use if ....else conditions for each new banks trying to implement.

2.Find area of the object

Not in open/closed Principle

public class Rectangle{  
   public double Height {get;set;}  
   public double Wight {get;set; }  
}  
public class Circle{  
   public double Radius {get;set;}  
}  
public class AreaCalculator  
{  
   public double TotalArea(object[] arrObjects)  
   {  
      double area = 0;  
      Rectangle objRectangle;  
      Circle objCircle;  
      foreach(var obj in arrObjects)  
      {  
         if(obj is Rectangle)  
         {    
            area += obj.Height * obj.Width;  
         }  
         else  
         {  
            objCircle = (Circle)obj;  
            area += objCircle.Radius * objCircle.Radius * Math.PI;  
         }  
      }  
      return area;  
   }  
}  

Open/ Closed Principle

public abstract class Shape  
{  
   public abstract double Area();  
} 

public class Rectangle: Shape  
{  
   public double Height {get;set;}  
   public double Width {get;set;}  
   public override double Area()  
   {  
      Console.WriteLine ("Rectangle");
      return Height * Width;  
   }  
}  
public class Circle: Shape  
{  
   public double Radius {get;set;}  
   public override double Area()  
   {  
       Console.WriteLine ("Circle");
      return Radius * Radus * Math.PI;  
   }  
}  
 
 /// Main class based on object it will call corresponding class method.

 public class AreaCalculator  
{  
   public double TotalArea(Shape[] arrShapes)  
   {  
      double area=0;  
      foreach(var objShape in arrShapes)  
      {  
         var shapearea = objShape.Area();  
         area+=shapearea;
         Console.WriteLine (shapearea);
      }  
      return area;  
   }  
}  

L: Liskov Substitution Principle

The Liskov Substitution Principle (LSP) states that "you should be able to use any derived class instead of a parent class and have it behave in the same manner without modification". It ensures that a derived class does not affect the behavior of the parent class, in other words,, that a derived class must be substitutable for its base class.

This principle is just an extension of the Open Closed Principle and it means that we must ensure that new derived classes extend the base classes without changing their behavior.

public class SqlFileManager  
{  
   public List<SqlFile? lstSqlFiles {get;set}  
   public string GetTextFromFiles()  
   {  
      StringBuilder objStrBuilder = new StringBuilder();  
      foreach(var objFile in lstSqlFiles)  
      {  
         objStrBuilder.Append(objFile.LoadText());  
      }  
      return objStrBuilder.ToString();  
   }  
   public void SaveTextIntoFiles()  
   {  
      foreach(var objFile in lstSqlFiles)  
      {  
         //Check whether the current file object is read-only or not.If yes, skip calling it's  
         // SaveText() method to skip the exception.  
  
         if(! objFile is ReadOnlySqlFile)  
         objFile.SaveText();  
      }  
   }  
}  

Here we altered the SaveTextIntoFiles() method in the SqlFileManager class to determine whether or not the instance is of ReadOnlySqlFile to avoid the exception. We can't use this ReadOnlySqlFile class as a substitute for its parent without altering SqlFileManager code. So we can say that this design is not following LSP. Let's make this design follow the LSP. Here we will introduce interfaces to make the SqlFileManager class independent from the rest of the blocks.

public interface IReadableSqlFile  
{  
   string LoadText();  
}  
public interface IWritableSqlFile  
{  
   void SaveText();  
}  

public class ReadOnlySqlFile: IReadableSqlFile  
{  
   public string FilePath {get;set;}  
   public string FileText {get;set;}  
   public string LoadText()  
   {  
      /* Code to read text from sql file */  
   }  
}  

public class SqlFile: IWritableSqlFile,IReadableSqlFile  
{  
   public string FilePath {get;set;}  
   public string FileText {get;set;}  
   public string LoadText()  
   {  
      /* Code to read text from sql file */  
   }  
   public void SaveText()  
   {  
      /* Code to save text into sql file */  
   }  
}  

public class SqlFileManager  
{  
   public string GetTextFromFiles(List<IReadableSqlFile> aLstReadableFiles)  
   {  
      StringBuilder objStrBuilder = new StringBuilder();  
      foreach(var objFile in aLstReadableFiles)  
      {  
         objStrBuilder.Append(objFile.LoadText());  
      }  
      return objStrBuilder.ToString();  
   }  
   public void SaveTextIntoFiles(List<IWritableSqlFile> aLstWritableFiles)  
   {  
        foreach(var objFile in aLstWritableFiles)  
        {  
            objFile.SaveText();  
        }  
   }  
}  

I: Interface Segregation Principle (ISP)

The Interface Segregation Principle states "that clients should not be forced to implement interfaces they don't use. Instead of one fat interface, many small interfaces are preferred based on groups of methods, each one serving one submodule.".

Example:

public Interface IScrum  
{  
   void CreateSubTask();  
   void AssginTask();  
   void WorkOnTask();  
}  

public class TeamLead : IScrum  
{  
   public void AssignTask()  
   {  
      //Code to assign a task.  
   }  
   public void CreateSubTask()  
   {  
      //Code to create a sub task  
   }  
   public void WorkOnTask()  
   {  
      //Code to implement perform assigned task.  
   }  
}  

public class Manager: IScrum  
{  
   public void AssignTask()  
   {  
      //Code to assign a task.  
   }  
   public void CreateSubTask()  
   {  
      //Code to create a sub task.  
   }  
   public void WorkOnTask()  
   {  
       //// here forced to implement so not in ISP
      throw new Exception("Manager can't work on Task");  
   }  
}  

Avoid to throw exception we split the interface

public interface IProgrammer  
{  
   void WorkOnTask();  
} 
public interface ILead  
{  
   void AssignTask();  
   void CreateSubTask();  
}  

public class Programmer: IProgrammer  
{  
   public void WorkOnTask()  
   {  
      //code to implement to work on the Task.  
   }  
}  
public class Manager: ILead  
{  
   public void AssignTask()  
   {  
      //Code to assign a Task  
   }  
   public void CreateSubTask()  
   {  
   //Code to create a sub taks from a task.  
   }  
}  

public class TeamLead: IProgrammer, ILead  
{  
   public void AssignTask()  
   {  
      //Code to assign a Task  
   }  
   public void CreateSubTask()  
   {  
      //Code to create a sub task from a task.  
   }  
   public void WorkOnTask()  
   {  
      //code to implement to work on the Task.  
   }  
}  

D: Dependency Inversion Principle

The Dependency Inversion Principle (DIP) states that high-level modules/classes should not depend on low-level modules/classes. Both should depend upon abstractions. Secondly, abstractions should not depend upon details. Details should depend upon abstractions.

Example: Exception log, error.log(exception ex) should be single function but within that based on cofiguration we alter storage place.

Not in DIP

public class DataExporter  
{  
   public void ExportDataFromFile()  
   {  
      try {  
         //code to export data from files to database.  
      }  
      catch(IOException ex)  
      {  
         new ExceptionLogger().LogIntoDataBase(ex);  
      }  
      catch(Exception ex)  
      {  
         new ExceptionLogger().LogIntoFile(ex);  
      }  
   }  
}  

DIP:

public class DataExporter  
{  
   public void ExportDataFromFile()  
   {  
      try {  
         //code to export data from files to database.  
      }  
      catch(Exception ex)  
      {  
         new ExceptionLogger().LogException(ex);  
      }  
     
   }  
}  

Public interface ILogger
{
    void LogException(Exception exception);
}
public class FileLog : ILogger
{  
   
   public void LogException()  
   {  
      //defalut logger
      ///logic for Write exception into files
   } 
}

public class ExceptionLogger  
{  
   private ILogger _logger; 
   public ExceptionLogger()  
   {  
      //defalut logger
      this._logger = new FileLog();  
   } 
   public ExceptionLogger(ILogger aLogger)  
   {  
      this._logger = aLogger;  
   }  
   public void LogException(Exception exception)  
   {  
       //based on implemeted logger it will log, Ex: log exception in DB,File,Mail etc
      this._logger.LogMessage(exception);  
   }  
  
}  

DotNetCore-MVC-SQL-Angular-Html

Tuesday 24 May 2022

.Net Core - Get appsettings..json data in class or controller

Request URL

Server response

Response body

Response headers

Request URL

Server response

Response body

Monday 9 May 2022

SOLID Principles in C#

O: Open/Closed Principle

L: Liskov Substitution Principle

I: Interface Segregation Principle (ISP)

D: Dependency Inversion Principle