实体框架5 DbUpdateException：非空值成员的空值

问题描述

我有一些数据模型：

[DataContract(Name = "artist")]
public class artist : IEqualityComparer<artist>
{
    [Key]
    [XmlIgnore]
    [DataMember]
    public int ID { get; set; }

    [DataMember]
    [XmlElement(ElementName = "name")]
    public string name { get; set; }

    [DataMember]
    [XmlElement(ElementName = "mbid", IsNullable = true)]
    public string mbid { get; set; }

    [DataMember]
    [XmlElement(ElementName = "url")]
    public string url { get; set; }

    [XmlElement(ElementName = "image", IsNullable = true)]
    public List<string> image { get; set; }

    [DataMember(IsRequired=false)]
    [XmlElement(ElementName = "stats", IsNullable = true)]
    public stats stats { get; set; }

    public double? match { get; set; }
    public List<tag> tags { get; set; }
    [XmlElement(ElementName = "similar")]
    [DataMember(Name = "similar")]
    public List<artist> similar { get; set; }

    [DataMember]
    [XmlElement(ElementName = "bio", IsNullable = true)]
    public wiki bio { get; set; }


    public bool Equals(artist x, artist y)
    {
        return x.name == y.name;
    }

    public int GetHashCode(artist obj)
    {
        return obj.name.GetHashCode();
    }
}

和复杂类型：

    [DataContract]
[ComplexType]
[XmlRoot(ElementName = "streamable", IsNullable = true)]
public class stats
{
    [DataMember(IsRequired = false)]
    public int listeners { get; set; }

    [DataMember(IsRequired = false)]
    public int playcount { get; set; }
}

和数据库包含：

[Table("CachedArtistInfo")]
public class MusicArtists
{
    [Key]
    public string artistName { get; set; }
    public artist artistInfo { get; set; }

    private DateTime _added = default(DateTime);
    [DataMember(IsRequired = true)]
    [Timestamp]
    public DateTime added
    {
        get
        {
            return (_added == default(DateTime)) ? DateTime.Now : _added;
        }
        set { _added = value; }
    }
}

最后一步：

        foreach (artist a in id)
        {
            df.CachedArtists.Add(new MusicArtists() { artistName = a.name, artistInfo = a });
            df.SaveChanges();
        }

错误：
ExceptionType
System.Data。 Entity.Infrastructure.DbUpdateException
非空值成员的空值。成员：'stats'。
一个变量是完全填充的，对象的统计信息在它里面。
怎么了？

ERROR: ExceptionType "System.Data.Entity.Infrastructure.DbUpdateException" "Null value for non-nullable member. Member: 'stats'."a variable is fully filled and object stats in it.what's wrong?

推荐答案

复杂类型不能为空 - 所以您必须在保存之前创建类的实例。这篇文章帮我解决了同样的问题。
http://weblogs.asp.net/manavi/archive/2011/03/28/associations-in-ef-4-1-code-first-part-2-complex-types.aspx

Complex types cannot be null - so you have to create an instance of the class before saving. This article helped me solve the same problem.http://weblogs.asp.net/manavi/archive/2011/03/28/associations-in-ef-4-1-code-first-part-2-complex-types.aspx

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