Ninject 2.1 ActivationException：激活字符串时出错

Question

我很困惑为什么在随机绑定中收到“Ninject.ActivationException：错误激活字符串没有可用的匹配绑定，并且类型不可自绑定”。如果我保留 IMedia 的绑定，它将抛出 ActivationException，但如果我使用 CallbackProvider，它就会起作用。所有这些类的结构都相同，但具有一些不同的属性。我很困惑为什么 ILocationType、IMedia 和 IFarmDataContext 会抛出 ActivationException 而其他的则不会。有什么想法吗？

/******************************
 * Core Types
 ******************************/
Bind<IFarmDataContext>().ToProvider(new CallbackProvider<IFarmDataContext>(delegate { return new FarmDataContext(); }));

//Media
Bind<IMedia>().To<Media>(); //blows up
//Bind<IMedia>().ToProvider(new CallbackProvider<IMedia>(delegate { return new Media(); }));
Bind<IMediaType>().To<MediaType>();
Bind<IMediaRelated>().To<MediaRelated>();

//Location
Bind<ILocation>().To<Location>();
Bind<ILocationType>().ToProvider(new CallbackProvider<ILocationType>(delegate { return new LocationType(); }));
Bind<ILocationDetail>().To<LocationDetail>();

Answer 1

Ninject 没有绑定要在 Media .ctor 中注入的“String key”；当它尝试创建依赖于 Media 的类型时，它不知道如何解决依赖关系并抛出异常。对于大多数类型，Ninject 会尝试为您创建一些东西，但是字符串和值类型不能自绑定，因为我们没有为它们提供良好的默认值，并且它可能会对使用不同基元约定的类型造成严重破坏。

您需要在绑定中添加参数值（.WithContructorArgument("key", someValue)）或使用某种提供程序（您已经完成）。

Answer 2

下面是 IMedia 接口和 Media 实现。 Media 是一个分部类，其主类是通过 LinqToSql DBML 文件生成的。上面绑定列表中列出的所有类型都是这种情况。

public interface IMedia : IValidationDictionary, IBaseDescriptor {

    /// <summary>
    /// Returns a specific Media object specifying 
    /// if you want the full or lite version
    /// </summary>
    /// <param name="id"></param>
    /// <param name="isLite"></param>
    /// <param name="context"></param>
    /// <returns></returns>
    IMedia Get(long id, bool isLite, DataContext context);

    /// <summary>
    /// Returns the lite version of the request Media object
    /// </summary>
    /// <param name="id"></param>
    /// <param name="context"></param>
    /// <returns></returns>
    IMedia Get(long id, DataContext context);

    /// <summary>
    /// Returns a list of Media Objects
    /// </summary>
    /// <param name="isLite"></param>
    /// <param name="context"></param>
    /// <returns></returns>
    ValidationList<IMedia> List(bool isLite, DataContext context);

    /// <summary>
    /// Returns a list of Media Objects with pagination capabilities
    /// </summary>
    /// <param name="isLite"></param>
    /// <param name="skip"></param>
    /// <param name="top"></param>
    /// <param name="context"></param>
    /// <returns></returns>
    ValidationList<IMedia> List(bool isLite, int skip, int top, DataContext context);

}

public partial class Media : BaseDescriptor, IMedia {

    #region Constructors

    public Media(String key, IError error)
        : base() {
        AddError(key, error);
    }

    #endregion

    #region Properties

    public MediaType Type {
        set { if (TypeID <= 0) { MediaType = value; } }
        get { return MediaType; }
    }

    #endregion

    #region Internal Methods

    /// <summary>
    /// Truncates relationships as appropriate to reduce over-the-wire size 
    /// </summary>
    protected override void MakeLite() {
        MediaRelateds = new EntitySet<MediaRelated>();
    }

    /// <summary>
    /// Validates the values and returns true if there are no problems.
    /// </summary>
    override public bool Validate() {
        this.ClearErrors();
        if (this.TypeID <= 0) { this.AddError("TypeID", new Error(ErrorType.VALIDATION, "TypeID is missing or invalid")); }
        if (string.IsNullOrEmpty(this.Path)) { this.AddError("Path", new Error(ErrorType.VALIDATION, "Path is missing or invalid")); }
        if (this.CreatedOn.Year <= 1900) { this.AddError("CreatedOn", new Error(ErrorType.VALIDATION, "CreatedOn is missing or invalid")); }
        if (this.CreatedBy <= 0) { this.AddError("CreatedBy", new Error(ErrorType.VALIDATION, "CreatedBy is missing or invalid")); }
        if (this.UpdatedOn.Year <= 1900) { this.AddError("UpdatedOn", new Error(ErrorType.VALIDATION, "UpdatedOn is missing or invalid")); }
        if (this.UpdatedBy <= 0) { this.AddError("UpdatedBy", new Error(ErrorType.VALIDATION, "UpdatedBy is missing or invalid")); }
        if (!string.IsNullOrEmpty(this.Path) && this.Path.Length > 255) { this.AddError("Path", new Error(ErrorType.VALIDATION, "Path is longer than the maximum of 255 characters")); }
        return (this.ErrorCount == 0);
    }
    #endregion


    #region Public Methods

    public ValidationList<IMedia> List(bool isLite, DataContext context) {
        return List(isLite, 0, 0, context);
    }

    public ValidationList<IMedia> List(bool isLite, int skip, int top, DataContext context) {
        if (context == null) { context = new DataContext(); }
        var query = context.Medias.Where(x => x.DeletedOn == null);
        List<Media> results;
        if (skip > 0 || top > 0) {
            if (top > 0) {
                if (skip < 0) { skip = 0; }
                results = query.OrderBy(x => x.ID).Skip(skip).Take(top).ToList();
            } else {
                results = query.OrderBy(x => x.ID).Skip(skip).ToList();
            }
        } else {
            results = query.OrderBy(x => x.ID).ToList();
        }

        var finalResult = new ValidationList<IMedia>(new List<IMedia>());
        foreach (var result in results) {
            result.IsLite = isLite;
            finalResult.Source.Add(result);
        }
        return finalResult;
    }

    public IMedia Get(long id, DataContext context) {
        return Get(id, false, context);
    }

    public IMedia Get(long id, bool isLite, DataContext context) {
        if (context == null) { context = new DataContext(); }
        var results = context.Medias.Where(x => x.ID == id && x.DeletedOn == null).ToList();
        var result = (results.Count > 0 ? results[0] : null);
        if (result != null) {
            result.IsLite = isLite;
        }
        return result;
    }

    #endregion

}