你调用的对象是空的。 C＃接口

Question

I know this question has been asked quite a few times, and I know the reason I am getting the error is because LicenseInfoRepository is null, but I am not sure how to fix it.

public abstract class VendorCodeGeneratorBase
{

    protected ILicenseInfoRepository LicenseInfoRepository;
    protected ICountryRegionRepository CountryRegionRepository;
    protected IEnumerable<IBrandModel> BrandModels;

    protected string GenerateVendorCodeUnEncoded(GenerateVendorCodeRequestModel requestModel)
    {
        int formatId = requestModel.VendorCodeFormat;
        var strToConvert = "";
        var brandBytes = new byte[5];
        var brands = LicenseInfoRepository.GetSubscriptionBrandsForVendorCode(requestModel.KeyNumber);

The error is happening on the line

var brands = LicenseInfoRepository.GetSubscriptionBrandsForVendorCode(requestModel.KeyNumber);

I don't know how to instantiate the class that implements the interface. This is the class

public class LicenseInfoRepository : ILicenseInfoRepository
{
    private readonly IEstDbContext _estDbContext;

    public LicenseInfoRepository(IEstDbContext estDbContext)
    {
        _estDbContext = estDbContext;
    }

    public List<VendorCodeSubscriptionBrandModel> 
    GetSubscriptionBrandsForVendorCode(int keyNumber)
    {
        return _estDbContext.SubscriptionBrands
            .Include(sb => sb.Brand)
            .Where(sb => sb.KeyNumber == keyNumber)
            .ProjectTo<VendorCodeSubscriptionBrandModel>()
            .ToList();
    }
}

I have a folder named repositories and inside that is the LicenseInfoRepository.cs class, and also inside that is a folder named Interfaces that has the ILicenseInfoRepository.cs interface. That interface looks like this:

namespace Data.Repositiories
{
    public interface ILicenseInfoRepository
    {
        List<VendorCodeSubscriptionBrandModel> 
GetSubscriptionBrandsForVendorCode(int keyNumber);
    }
}

Answer 1

In the same folder where you have LicenseInfoRepository.cs , you need an interface class ILicenseInfoRepository.cs :

using System;
using System.Collections.Generic;
using System.Data;
using System.Web.Mvc;
// Add/remove as appropriate

namespace YourProject.DAL // Change to your project / repository folder name
{
    public interface ILicenseInfoRepository : IDisposable
    {
        List<VendorCodeSubscriptionBrandModel> GetSubscriptionBrandsForVendorCode(int keyNumber);
        // Add any other methods that exist in LicenseInfoRepository.cs file
    }
}

There may lines missing in you VendorCodeGeneratorBase class, especially how you usually instantiate private ApplicationDbContext db = new ApplicationDbContext(); . After you add the interface, please share errors / details so we can continue fixing your code.