如何将.net框架数据层引用到.net核心控制台应用程序

Question

I am new to .NET Core. I already have a Web API application in .NET framework. This includes class library projects for my repository using Entity Framework.

Now I want to create a scheduler like service. I am planning to do it in .NET Core. For testing I created a sample .NET Core console application and added my old dll which contains my data layer code.

But when I run the console app, it shows an error as 'MyCon' not found. Please help me with this.

This is my console app code:

static void Main(string[] args)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);

    IConfigurationRoot configuration = builder.Build();

    Console.WriteLine("Hello World!...Scheduler starting....");
    Scheduler scheduler = new Scheduler();
}

The scheduler code looks like the following

public class Scheduler
{
    private readonly Timer _tmr = null;
    private readonly IUnitOfWork _unitOfWork = null;
    private static readonly HttpClient _httpClient = new HttpClient() { MaxResponseContentBufferSize = 1000000, Timeout = System.TimeSpan.FromSeconds(60) };

    public Scheduler()
    {
        try
        {
            _tmr = new Timer();
            _unitOfWork = new UnitOfWork();

            _tmr.Interval = 10000;
            _tmr.Elapsed += _tmr_Elapsed;
            _tmr.Start();
        }
        catch(Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        finally
        {
            _tmr = null;
        }
    }

    private void _tmr_Elapsed(object sender, ElapsedEventArgs e)
    {
        try
        {
            _tmr.Stop();

              /* My database interaction code here */

            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            _tmr.Start();
        }
    }
 }

The following is my configuration code(appsettings.:

{
    "ConnectionStrings": {
        "MyCon": "Data Source=myconnectionstring;"
    }
}

I don't know is this enough for EF to work.

I got the following error;

System.InvalidOperationException: No connection string named 'MyCon' could be found in the application config file.

at System.Data.Entity.Internal.LazyInternalConnection.Initialize()
at System.Data.Entity.Internal.LazyInternalConnection.get_Connection()
at Microsoft.AspNet.Identity.EntityFramework.IdentityDbContext 1.IsIdentityV1Schema(DbContext db)
at Microsoft.AspNet.Identity.EntityFramework.IdentityDbContext 1.IsIdentityV1Schema(DbContext db)
at Microsoft.AspNet.Identity.EntityFramework.IdentityDbContext 1.IsIdentityV1Schema(DbContext db)
at Microsoft.AspNet.Identity.EntityFramework.IdentityDbContext 1..ctor(String nameOrConnectionString, Boolean throwIfV1Schema)
at MyProj.Data.Context.MyContextContext..ctor()
at MyProj.Repositories.UnitOfWork..ctor()
at Engager.Scheduler..ctor() in C:\\Users\\akhilraj.rajendran\\Documents\\Visual Studio 2017\\Projects\\Sample\\Sample\\Scheduler.cs:line 29}

Answer 1

I'm writing an answer since I do not have enough reputation to add a comment. From the information you provided it is not clear how you are reading the connection string. try adding below code in your Main function and check whether connection string is read or not from appsetting.json file.

IConfigurationRoot configuration = builder.Build();
var connstring = configuration.GetConnectionString("MyCon");

Here is a great blog that will help you with reading appsettings.json in a .Net Core console application.

https://blog.bitscry.com/2017/05/30/appsettings-json-in-net-core-console-app/

Now this is off topic, but, If you want to create a schedulers in .Net Core, you should definitely check out HangFire .

Hangfire is an easy way to perform background processing in .NET and .NET Core applications. No Windows Service or separate process required. Backed by persistent storage. Open and free for commercial use. Hangfire handles all the scheduling part so you can focus on writing jobs.