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我在这里束手无策。问题是我试图在数据库中创建一个新实体，使用 db 生成的标识属性，在 LINQ to SQL 中，然后创建另一个与第一个实体相关联的实体。我猜问题是 LINQ to SQL 无法插入第二个实体，而没有来自第一个实体的 id，直到数据库生成它才会知道。

有没有其他人遇到过这个问题...如果是这样，您是如何解决的？我知道我可以SubmitChanges在创建第一个和第二个实体之间调用，但这会破坏程序的事务完整性。

这是一个具体的例子：

[Table(Name = "Searches")]
public class Search
{
    // Db Generated Key
    [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
    public Int32 SearchID { get; set; }

    // Each search can have multiple search parameters
    private EntitySet<SearchParam> searchParams;

    [Association(Storage = "searchParams", ThisKey = "SearchID", OtherKey = "SearchID")]
    public EntitySet<SearchParam> SearchParams
    {
        get
        {
            return searchParams;
        }
        set
        {
            searchParams.Assign(value);
        }
    }
}

[Table(Name = "SearchParams")]
public class SearchParam
{
    [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
    public Int32 SearchParamID { get; set; }

    [Column]
    public String ParamValue { get; set; }

    // Each search param is associated with one search
    [Column]
    public Int32 SearchID { get; set; }

    private EntityRef<Search> search = new EntityRef<Search>();

    [Association(Storage = "search", ThisKey = "SearchID", OtherKey = "SearchID", IsForeignKey = true)]
    public Search Search
    {
        get
        {
            return search.Entity;
        }
        set
        {
            search.Entity = value;
        }
    }
}

因此，使用上面的代码，如果我要执行以下操作，.NET 会给我一个NullReferenceExceptionon SubmitChanges：

using (SampleDataContext context = new SampleDataContext())
{
    Search search = new Search();
    search.SearchParams.Add(new SearchParam() { ParamValue = "...paramvalue..." });
    context.Searches.InsertOnSubmit(search);
    context.SubmitChanges();
}
4

3 回答 3

0

不知道为什么你的不工作，但这应该工作

using (SampleDataContext context = new SampleDataContext())
{
     Search search = new Search();
     SearchParam param = new SearchParam() { ParamValue = "...paramvalue..." })
     param.search = search
     context.searchparams.InsertOnSubmit (param ) // Not sure if this is necessary
     context.Searches.InsertOnSubmit(search);
     context.SubmitChanges();
}

一站式交易。

于 2013-09-18T10:25:36.867 回答
0

在我看来，您并没有SearchParams在调用列表之前add对其进行初始化。这是否有效：

using (SampleDataContext context = new SampleDataContext()) {
    Search search = new Search();
   search.SearchParams = new EntitySet<SearchParam>(); //<-- THIS LINE
    search.SearchParams.Add(new SearchParam() { ParamValue = "...paramvalue..." });
    context.Searches.InsertOnSubmit(search);
    context.SubmitChanges();
}
于 2013-09-20T17:54:02.167 回答
0

尝试将以下内容添加到您的搜索类

    public Search()
    {
        this.SearchParams = new EntitySet<SearchParams >(
         new Action<SearchParams >(this.attach_SearchParams ), 
         new Action<SearchParams >(this.detach_SearchParams ));
    }

    private void attach_SearchParams(SearchParams sp)
    {
        sp.Search = this;
    }

    private void detach_Search(SearchParams sp)
    {
        sp.Search = null;
    }
于 2013-09-20T18:57:44.410 回答