.NET Core调试时IOrderHelp服务解析失败异常求助

调试.NET Core的C#项目时触发未处理异常，错误信息：

An unhandled exception occurred while processing the request
InvalidOperationException: Unable to resolve service for type 'PlatformWebApi.Controllers.Order.IOrderHelp' while attempting to activate
PlatformWebApi.Controllers.Order.OrderApi
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired)

相关代码：

OrderApi.cs #

namespace PlatformWebApi.Controllers.Order
{
    [Authorize(AuthenticationSchemes = JwtBearerDefaults.AuthenticationScheme)]
    public class OrderApi: Controller
    {
        public Log log = new Log();
        private readonly WebOptions _webOption;
        private IWebApiHelp _WebApiHelp;
        private ISapFunction _sapFunction;
        private readonly  IOrderHelp _orderHelp;
        public OrderApi(IOptions<WebOptions> myConfiguration,
           IWebApiHelp WebApiHelp,
           ISapFunction SapFunction,
           IOrderHelp OrderHelp)
        {
            _webOption = myConfiguration.Value;
            _WebApiHelp = WebApiHelp;
            _orderHelp = OrderHelp;
            _sapFunction = SapFunction;
        }
        [HttpPost(ApiRoutes.Order.AddUpdateOrder)]
        [Consumes("application/xml", "application/json")]
        public ResponseData AddUpdateOrder([FromBody] OrderXml.OrderDetails xmlString)
        {
            ResponseData oRes = _orderHelp.Add_updateOrder(xmlString);
            return oRes;//Json(oRes);
        }
    }
}

IOrderHelp.cs #

namespace PlatformWebApi.Controllers.Order
{
    public interface IOrderHelp
    {
        ResponseData Add_updateOrder(OrderXml.OrderDetails xmlString);
    }
}

OrderHelp.cs #

public class OrderHelp :IOrderHelp
{
    string error = "";
    public Log log = new Log();
    private readonly WebOptions _webOption;
    private IWebApiHelp _WebApiHelp;
    private ISapFunction _sapFunction;
    private ISAPConnectionHelp _SAPConnectionHelp;

    public OrderHelp(IOptions<WebOptions> myConfiguration,
       IWebApiHelp WebApiHelp,
       ISapFunction SapFunction,
       ISAPConnectionHelp SAPConnectionHelp)
    {
        _webOption = myConfiguration.Value;
        _WebApiHelp = WebApiHelp;
        _sapFunction = SapFunction;
        _SAPConnectionHelp = SAPConnectionHelp;
    }
    public ResponseData Add_updateOrder(OrderXml.OrderDetails xmlString)
    {
        string sErrorMsg = "";
        int DocEntry = 0, res = 0;
        List<ResponseKeys> oListResponseKeys = new List<ResponseKeys>();
        ResponseData oResponseData = new ResponseData();

        SAPbobsCOM.Documents oOrder = (Documents)_SAPConnectionHelp.GetCompany().GetBusinessObject(BoObjectTypes.oOrders);
        // 省略后续代码
    }
}

这个异常是因为.NET Core依赖注入容器中未注册IOrderHelp接口与它的实现类OrderHelp，导致框架无法创建OrderApi控制器实例。

需要在项目的服务配置文件中添加注册代码：

.NET 6+（Program.cs） #

在builder.Build()之前添加：

// 注册IOrderHelp与实现类
builder.Services.AddScoped<IOrderHelp, OrderHelp>();
// 同时确保其他依赖服务已注册，替换为你的实际实现类
builder.Services.AddScoped<IWebApiHelp, WebApiHelp>();
builder.Services.AddScoped<ISapFunction, SapFunction>();
builder.Services.AddScoped<ISAPConnectionHelp, SAPConnectionHelp>();

.NET Core 3.x及更早版本（Startup.cs） #

在ConfigureServices方法中添加：

public void ConfigureServices(IServiceCollection services)
{
    // 其他服务注册代码...
    services.AddScoped<IOrderHelp, OrderHelp>();
    services.AddScoped<IWebApiHelp, WebApiHelp>();
    services.AddScoped<ISapFunction, SapFunction>();
    services.AddScoped<ISAPConnectionHelp, SAPConnectionHelp>();
}

生命周期选择说明：

• AddScoped：每个请求创建一个实例，适配Web API控制器场景
• AddTransient：每次获取服务时创建新实例
• AddSingleton：应用生命周期内仅创建一个实例

Web API场景下优先使用AddScoped即可。

内容的提问来源于stack exchange，提问作者Esther