依赖注入场景下继承接口无法访问扩展方法的解决方案咨询

你的判断是对的，基类BaseEntityWebApiProvider中声明的_logicProvider是IBaseEntityLogicProvider<TEntity>类型，而非泛型参数TLogicProvider，因此无法直接访问子接口IAuthorLogicProvider的专属方法。以下是几种可行的解决方式：

方式一：修改基类字段类型为泛型参数TLogicProvider #

直接调整基类中_logicProvider的类型，使其使用泛型参数TLogicProvider而非父接口类型，这样子类就能直接调用子接口的方法：

[ApiController]
[Route("Api/V1/[controller]")]
public abstract class BaseEntityWebApiProvider<TEntity, TLogicProvider> : ControllerBase
    where TEntity : BaseEntity
    where TLogicProvider : IBaseEntityLogicProvider<TEntity> 
{
    #region [ Fields ]
    protected readonly ILogger<BaseEntityWebApiProvider<TEntity, TLogicProvider>> _logger;
    // 将类型改为TLogicProvider
    protected readonly TLogicProvider _logicProvider;
    #endregion

    #region [ CTor ]
    public BaseEntityWebApiProvider(ILogger<BaseEntityWebApiProvider<TEntity, TLogicProvider>> logger,
        TLogicProvider logicProvider) {

        this._logger = logger;
        this._logicProvider = logicProvider;
    }
    #endregion
}

修改后，AuthorController中的this._logicProvider.GetListByBookIdAsync(bookId)可直接正常编译调用，无需额外改动。

方式二：在子类中进行类型转换 #

若不想修改基类，可在子类中将_logicProvider强制转换为IAuthorLogicProvider类型后再调用方法：

[HttpGet(nameof(MethodUrl.GetListByBookId) + "/{BookId}")]
public async Task<IActionResult> GetListByBookIdAsync(string bookId) {
    try {
        // 转换为具体的子接口类型
        var authorLogicProvider = (IAuthorLogicProvider)this._logicProvider;
        var result = await authorLogicProvider.GetListByBookIdAsync(bookId);

        if (result == null || result.Count() <= 0) {
            return NotFound("Empty");
        }

        return Ok(result);
    } catch (ArgumentNullException ex) {
        this._logger.LogError(ex.Message);
        return BadRequest();
    } catch (Exception ex) {
        this._logger.LogError(ex.Message);
        return new StatusCodeResult(StatusCodes.Status500InternalServerError);
    }
}

注意：此方式需确保注入的_logicProvider确实是IAuthorLogicProvider的实现类，否则会抛出InvalidCastException。

方式三：在基类中添加类型安全的转换属性 #

可在基类中封装一个类型转换的属性，避免子类重复编写转换逻辑：

[ApiController]
[Route("Api/V1/[controller]")]
public abstract class BaseEntityWebApiProvider<TEntity, TLogicProvider> : ControllerBase
    where TEntity : BaseEntity
    where TLogicProvider : IBaseEntityLogicProvider<TEntity> 
{
    #region [ Fields ]
    protected readonly ILogger<BaseEntityWebApiProvider<TEntity, TLogicProvider>> _logger;
    protected readonly IBaseEntityLogicProvider<TEntity> _logicProvider;
    #endregion

    // 添加类型转换属性
    protected TLogicProvider TypedLogicProvider => (TLogicProvider)_logicProvider;

    #region [ CTor ]
    public BaseEntityWebApiProvider(ILogger<BaseEntityWebApiProvider<TEntity, TLogicProvider>> logger,
        TLogicProvider logicProvider) {

        this._logger = logger;
        this._logicProvider = logicProvider;
    }
    #endregion
}

随后在子类中使用该属性调用方法：

var result = await this.TypedLogicProvider.GetListByBookIdAsync(bookId);

这种方式既保留了基类原有的_logicProvider字段，又能安全访问子接口方法，同时避免子类重复编写转换代码。

内容的提问来源于stack exchange，提问作者thanh n. van