Wrapper Class?

Question

Wrapper Class?

Ronald Rex 1,666

Can someone please give me an example a using an Interface inside of a class and what is the code below called? wrapping a class inside of another class? Thanks !!!!!

public IDbConnection CreateDatabaseConnection()
=> new SqlConnection(_connectionString);

public class DapperContext  
    {  
        private readonly IConfiguration _configuration;  
        private readonly string _connectionString;  
        public DapperContext(IConfiguration configuration)  
        {  
            _configuration = configuration;  
            _connectionString = _configuration.GetConnectionString("SqlConnection");  
        }  
        public IDbConnection CreateDatabaseConnection()  
            => new SqlConnection(_connectionString);  
              
  
          
    }

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Answer 1

AgaveJoe 30,126

The code sample looks like standard asp.net dependency injection pattern. The _configuration variable is just a field within the DapperContext class.

Fields (C# Programming Guide)

The _configuration field implements IConfiguration. The implementation (code) can read asp.net configuration. This is simply part of asp.net configuration that comes with the framework.

Configuration in ASP.NET Core

Ronald Rex 1,666 Reputation points

2022-07-26T17:21:26.897+00:00

I am referring to this line of code.....

public IDbConnection CreateDatabaseConnection()
=> new SqlConnection(_connectionString);

Where it is subsequently injected into a Repository. Do you understand?

public class CompanyRepository : ICompanyRepository
{
private readonly DapperContext _context;
public CompanyRepository(DapperContext context)
{
_context = context;
}
public async Task<IEnumerable<Company>> GetCompanies()
{
var query = "SELECT * FROM Companies";
using (var connection = _context.CreateDatabaseConnection())
{
var companies = await connection.QueryAsync<Company>(query);
return companies.ToList();
}
}
}

I was wondering what is this called? wrapping an interface in a class? I just need to know how to set this up so i can get a working example that I constructed. I couldnt see an implementation for the IDbConnection interface and it let me use any method. I am just trying to find out again how I can get my own working example rather than just understanding what is happening in this code. Thanks !!!!
AgaveJoe 30,126 Reputation points

2022-07-26T18:08:54.077+00:00
The line of code in question is a standard C# method that returns an implementation of IDbConnection which in this case is SqlConnection().

public IDbConnection CreateDatabaseConnection() => new SqlConnection(_connectionString);

The following method is the same as above.

public IDbConnection CreateDatabaseConnection() { return new SqlConnection(_connectionString); }

The repository class is using the same standard dependency injection pattern to inject the DapperContext. The GetCompanies() method is simply calling the CreateDatabaseConnection() method which is a method in the DapperContext class. This a fundamental C# method construct.

Methods (C# Programming Guide)

public static async Task Main() { MyClass c = new MyClass(); c.MyClassMethod(); } public class MyClass { public void MyClassMethod() { Console.WriteLine("Hello from MyClassMethod"); } }

Results

Hello from MyClassMethod

Answer 2

I see what is confusing you, so this line of code:

public IDbConnection CreateDatabaseConnection()  => new SqlConnection(_connectionString);

It is just a method using lamba expresion and it is equivalent to:

 public IDbConnection CreateDatabaseConnection()  
 {  
        return new SqlConnection(_connectionString);  
 }

It is returning a Class ( SqlConnection) which should be implementing IDbConnection Interface, that's it.

To answer your question if it is called:

wrapping an interface in a class?

Nop, that is just normal interface-class behavior from always. I mean you can use Interface as a "Type" instead of the class "Type" to make your method more "flexible", and It could help you if you create new implementations of the same interface or while you test the code.

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Wrapper Class?

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