尝试调用接口服务时抛出控制器错误 "An object Reference is required for the non-static field"

Question

我目前正在为我的网站构建一个 API 应用程序，以便在我的网站和数据库之间建立连接。我还使用了一个 3 层架构（我有 1 个控制器，里面有来自 Azure Function 的 HttpTrigger，我有一个用于调用我的数据库查询的服务，我有一个存储库，我可以在其中进行查询数据库）。

所以这个结构是这样工作的：控制器 (HttpTrigger) - 调用服务服务调用存储库存储库 - 执行对我的数据库的查询和 returns 要服务的值。

我正在尝试实现依赖注入的概念，我确实认为它在工作，因为我已经添加了一个 Startup.cs 文件来调用我的接口和 class实现我的界面。

问题是：在控制器上，我正在初始化我的接口，但是当我尝试从我的服务调用方法时，它抛出以下错误：“非静态字段需要对象引用, 方法或属性 'AlunoController.alunoService'"

这些是我的文件：

IAlunoService - 接口

public interface IAlunoService
{
    public Task<IList<AlunoModel>> ObterAlunos();
}

AlunoService - 实现接口方法

public class AlunoService : IAlunoService
{
        #region DI services
        private readonly ILogger<AlunoService> logger;
        private readonly IAlunoRepository alunoRepository;

        public AlunoService(
            ILogger<AlunoService> logger,
            IAlunoRepository alunoRepository
            )
        {
            this.logger = logger;
            this.alunoRepository = alunoRepository;

        }
        #endregion

        public async Task<IList<AlunoModel>> ObterAlunos()
        {
            Utility.WriteLog(Utility.LogType.Information, "Service - ObterAlunos Called");

            var alunos = await alunoRepository.ObterAlunos();
            if(alunos == null)
            {
                throw new NullReferenceException();
            }

            return alunos;
        }
}

Startup.cs 文件

    [assembly: WebJobsStartup(typeof(ProjetoGlobalHajime_APILayer.Startup))]
namespace ProjetoGlobalHajime_APILayer
{
    public class Startup : IWebJobsStartup
    {
        public void Configure(IWebJobsBuilder builder)
        {
            builder.Services.AddScoped<IAlunoService, AlunoService>();
builder.Services.AddScoped<IAlunoRepository, AlunoRepository>();
        }
    }
}

AlunoController - 这就是我遇到问题的地方

#region DI Services
    private readonly IAlunoService alunoService;
    #endregion

    public AlunoController(IAlunoService alunoService, ILogger<AlunoController> log)
    {
        this.alunoService = alunoService;
        IAlunoService alunoService1 = alunoService;
    }

    /// <summary>
    /// Retorna todos os alunos
    /// </summary>
    /// <param name="req"></param>
    /// <param name="log"></param>
    /// <returns></returns>
    [FunctionName("Aluno_Obter_Lista")]
    public static async Task<IActionResult> Alunos_ObterLista(
        [HttpTrigger(AuthorizationLevel.Function, "get", Route = "Aluno/ObterLista")] HttpRequest req,
        ILogger log)
    {
        log.LogInformation("Alunos_Obter_Lista Called");

        try
        {
            alunoService.ObterAlunos(); //----------> The error is being thrown here
        }
        catch (Exception ex)
        {
            log.LogError("[ERROR] " + ex.InnerException);
        }

        return new OkObjectResult("Anything");
    }

IAlunoRepository

public interface IAlunoRepository
    {
        public Task<IList<AlunoModel>> ObterAlunos();
    }

AlunoRepository

public class AlunoRepository : IAlunoRepository
    {
        public async Task<IList<AlunoModel>> ObterAlunos()
        {
            List<AlunoModel> listaAlunos = new List<AlunoModel>();
            using (SqlConnection connection = new SqlConnection(Utility.ConnectDatabaseString()))
            {
                await connection.OpenAsync();
                SqlCommand command = new SqlCommand("SELECT * FROM dbo.aluno", connection);
                using (SqlDataReader reader = await command.ExecuteReaderAsync())
                {
                    while (reader.Read())
                    {
                        try
                        {
                            listaAlunos.Add(new AlunoModel { Id = reader.GetInt32(0), Nome = reader.GetString(1), Data_Nascimento = reader.GetDateTime(2), Contacto = reader.GetString(3), Morada = reader.GetString(4), C_Postal = reader.GetString(5), Localidade = reader.GetString(6), Email = reader.GetString(7), Nif = reader.GetInt32(8), Recolha_Imagem = reader.GetByte(9), Atestado_Medico = reader.GetByte(10), Protecao_Dados = reader.GetByte(11), Cartao_Cidadao = reader.GetString(12), Validade = reader.GetDateTime(13), Fk_encarregado_educacao_id = reader.GetInt32(14), Fk_turma_id = reader.GetInt32(15) });
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine("[ERROR] Exception Found: " + ex.InnerException);
                            Utility.WriteLog(Utility.LogType.Error, ex.InnerException.ToString());
                        }
                    }
                }
                connection.Close();

            }
            return listaAlunos;
        }
    }

我正在努力理解为什么这不起作用，因为我在我的 Controller Constructor 上调用了接口。虽然没用。

奇怪的是，我使用相同的“方式”来调用和实现服务文件上的接口，例如，我可以毫无问题地调用“alunoRepository”。

你能帮我解决这个问题吗？我目前正在上大学，这与我的期末项目之一有关。

编辑：错误的屏幕截图：

Answer 1

如果您没有正确使用 reader，您将得到空对象。您必须以这种方式使用异步 reader：

 while (await reader.ReadAsync()) {
    for (int i = 0; i < reader.FieldCount; i++) {
         // Process each column as appropriate
          object obj = await reader.GetFieldValueAsync<object>(i);
        }
}

而且因为你到处都在使用异步方法，所以你必须调用 Alunos_ObterLista.ObterAlunos as async:


var resultList = await alunoService.ObterAlunos();

.....
return new OkObjectResult(resultList );

Answer 2

我想出了问题所在。一整天都在看它，却没有意识到我是在静态方法中调用非静态方法。

在我的控制器中，我刚刚删除了“静态”，它就像一个魅力。感谢大家的意见。

尝试调用接口服务时抛出控制器错误 "An object Reference is required for the non-static field"

Controller Error "An object Reference is required for the non-static field" is being thrown when trying to call interface Service

c#

dependency-injection

interface