What is Dependency in C#?

Ashish Verma

10y1.3k.NET

How a class dependent to another class? Any example so that clearly explain in interview.

Now what is Dependency injection? they reduces tightly coupled to loosley coupled so, code maintaince is easy so how any example?

5 Replies

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Vinay Singh10y ago
When you use use interface class in a class at that time you need to use the implement the interface.
Now what is Dependency injection ?
Dependency injection is used to create a single instance for a class at the time of accessing the application. so no requirement of creating instance again and again
Sandeep Singh Shekhawat10y ago
Ashish, Follow the link mentioned in theprevious thread in which mentioned practical andreal life example.
Ashish Verma10y ago
Hi,
I know what is dependency Injection and how many type we can implement but i want to know easy example so can explain it better way.
Manas Mohapatra10y ago
Dependency Injection (DI) is a design pattern that allow us to develop loosely coupled code.
DI is a great way to reduce tight coupling between software components.

It can be implemented in following ways:

Through Constructor
Through Method
Through Property
We will implement Dependancy Injectio using constructor:

public class ExcpetionLogger
{
    private ILogger _logger;

    public ExcpetionLogger(ILogger aLogger)
    {
      this._logger = aLogger;
    }

    public void LogException(Exception aException)
    {
      this._logger.WriteToLog(aException.Message);
    }
}

public interface ILogger
{
    void WriteToLog(string text);
}

public class LogToFile : ILogger
{
    public void WriteToLog(string text)
    {
        Console.WriteLine("Writing data in text file: " + text);
    }
}

public class LogToDB : ILogger
{
    public void WriteToLog(string text)
    {
        Console.WriteLine("Writing data in DB: " + text);
    }
}
Let's call the method:
try
{
   //code to export data from files to database.
}
catch(IOException ex)
{
    ExcpetionLogger excpetion1 = new ExcpetionLogger(new LogToFile());
    excpetion1.LogException(ex);// Writing data in text file:

    ExcpetionLogger excpetion2 = new ExcpetionLogger(new LogToDB());
    excpetion2.LogException(ex); // Writing data in DB:
}
In preceding code we are passing the instance of Loggerer class through constructor. And it logs the the exception message based object instance. First we are passing to log the messge and secondly we are passing to log message in DB. It is totally independent.
You can also implement dependency injection using third party library like autofac, microsoft, Ninject etc..
Sandeep Singh Shekhawat10y ago
Dependency Injection (DI) is a pattern where objects are not responsible for creating their own dependencies. Dependency injection is a way to remove hard-coded dependencies among objects, making it easier to replace an object's dependencies, either for testing (using mock objects in unit test) or to change run-time behavior.

There are three types of dependency injections:
1. Constructor Dependency Injection
2. Setter Dependency Injection
3. Interface Dependency Injection
There are some articles which explained dependencyinjection and Inversion of control. Please have a look on below.

1.http://www.c-sharpcorner.com/UploadFile/3d39b4/constructor-dependency-injection-pattern-implementation-in-c/

2. http://www.c-sharpcorner.com/UploadFile/3d39b4/crud-operations-using-the-generic-repository-pattern-and-dep/

3.http://www.c-sharpcorner.com/article/dependency-inject-using-ninject-ioc-in-console-application/

You can download source code as well to follow below links:
1.https://gallery.technet.microsoft.com/CRUD-Operations-Using-0aa46470
2.https://code.msdn.microsoft.com/Dependency-Injection-in-e7adb082