实体框架神秘错误答案

【问题标题】：Entity Framework mysterious error实体框架神秘错误
【发布时间】：2016-03-03 13:00:20
【问题描述】：

请帮忙。我不明白为什么从我的实体上下文中

var stagesExist = context.WfwDocumentWorkStages
   .Any(it => it.Enabled && it.ExecutionId == execution.Id
   && it.Level == execution.Level && it.ResultId == null);

value stageExist 为 false 但是

var stages = context.WfwDocumentWorkStages.Where(it => it.Enabled 
   && it.ExecutionId == execution.Id
   && it.Level == execution.Level).ToList();
bool stagesExist = stages.Any(it=>it.ResultId == null);

value stagesExist 是真的吗？？

【问题讨论】：

请尝试将第一个实现中的最后一个子句更改为&& it.ResultId == null。我认为您正在以不同的值再次捕获it...
这里只是一个错字

标签： entity-framework

【解决方案1】：

SQL 探查器显示此查询

SELECT 
CASE WHEN ( EXISTS (SELECT 
    1 AS [C1]
    FROM  ( SELECT 1 AS X ) AS [SingleRowTable2]
    WHERE 1 = 0
)) THEN cast(1 as bit) ELSE cast(0 as bit) END AS [C1]
FROM  ( SELECT 1 AS X ) AS [SingleRowTable1]

为什么实体框架不能正常工作？？？

【讨论】：

【解决方案2】：

型号：

public partial class WfwDocumentWorkScheme : EnabledEntity
{
    public WfwDocumentWorkScheme()
    {
        this.WfwExecutionEvents = new List<WfwExecutionEvent>();
    }

    public int ExecutionId { get; set; }
    public int Level { get; set; }
    public int? RoleId { get; set; }
    public string CoordinatorSid { get; set; }
    public DateTimeOffset? Date { get; set; }
    public int? ResultId { get; set; }
    public string Comment { get; set; }
    public virtual Employee Coordinator { get; set; }
    public virtual EmployeeRole EmployeeRole { get; set; }
    public virtual WfwEventResult WfwEventResult { get; set; }
    public virtual WfwDocumentExecution WfwDocumentExecution { get; set; }
    public virtual ICollection<WfwExecutionEvent> WfwExecutionEvents { get; set; }
}

映射

public class WfwDocumentWorkSchemeMap : EntityTypeConfiguration<WfwDocumentWorkScheme>
{
    public WfwDocumentWorkSchemeMap()
    {
        // Primary Key
        this.HasKey(t => t.Id);

        // Properties
        this.Property(t => t.CoordinatorSid)
            .HasMaxLength(46);

        // Table & Column Mappings
        this.ToTable("WfwDocumentWorkSchemes");
        this.Property(t => t.Id).HasColumnName("Id");
        this.Property(t => t.ExecutionId).HasColumnName("ExecutionId");
        this.Property(t => t.Level).HasColumnName("Level");
        this.Property(t => t.RoleId).HasColumnName("RoleId");
        this.Property(t => t.CoordinatorSid).HasColumnName("CoordinatorSid");
        this.Property(t => t.Date).HasColumnName("Date");
        this.Property(t => t.ResultId).HasColumnName("ResultId");
        this.Property(t => t.Comment).HasColumnName("Comment");
        this.Property(t => t.Enabled).HasColumnName("Enabled");

        // Relationships
        this.HasRequired(t => t.Coordinator)
            .WithMany(t => t.WfwDocumentWorkSchemes)
            .HasForeignKey(d => d.CoordinatorSid);
        this.HasRequired(t => t.WfwDocumentExecution)
            .WithMany(t => t.WfwDocumentWorkSchemes)
            .HasForeignKey(d => d.ExecutionId);
        this.HasRequired(t => t.WfwEventResult)
            .WithMany(t => t.WfwDocumentWorkSchemes)
            .HasForeignKey(d => d.ResultId);
        this.HasOptional(t => t.EmployeeRole)
            .WithMany(t => t.WfwDocumentWorkSchemes)
            .HasForeignKey(d => d.RoleId);
    }
}

结果模型包含虚拟列表

public class WfwEventResult : EnabledEntity
{
    public WfwEventResult()
    {
        this.WfwExecutionEvents = new List<WfwExecutionEvent>();
        this.WfwDocumentWorkSchemes = new List<WfwDocumentWorkScheme>();
    }

    public string Name { get; set; }
    public string Description { get; set; }
    public bool Success { get; set; }
    public virtual ICollection<WfwExecutionEvent> WfwExecutionEvents { get; set; }
    public virtual ICollection<WfwDocumentWorkScheme> WfwDocumentWorkSchemes { get; set; }
}

【讨论】：

最好修改你原来的问题，而不是把它作为答案。
谢谢！下次做

【解决方案3】：

问题在于您的映射中的这一行：

this.HasRequired(t => t.WfwEventResult)

您实际上是在告诉 EF 关联的 FK 列永远不会是 null（尽管您已经将其设为 int? 并且记录具有 null 值）。请记住，EF 在构建 SQL 查询时使用元数据信息，在这种情况下，我猜查询优化器决定此查询永远不会返回记录（类似于 .Where(it => false)）并生成您看到的假 SQL 查询。

很快 - 确保您始终向 EF 提供正确的信息。在这种情况下，将上面的内容更改为

this.HasOptional(t => t.WfwEventResult)

您会看到不同的（真实的）查询并得到正确的结果。

【讨论】：