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确定Linq到Sql查询的源DataContext

datacontext linq-to-sql linq .net

Rune Grimstad · 技术社区 · 16 年前

DataContext.SubmitChanges();

有没有办法确定查询来自哪个DataContext?DataQuery类本身被标记为internal,因此我无法访问它的上下文属性而不诉诸丑陋的反射黑客,因此我正在寻找一种更干净的方法。

有(几种)方法可以解决这个问题,例如传递对源DataContext的引用,但我想一定有一种更简单的方法可以做到这一点。

编辑: 下面的代码可以工作,但很难看:

FieldInfo contextField = query.GetType().GetField("context", BindingFlags.Instance | BindingFlags.NonPublic);
if (query != null)
{
  queryContext = contextField.GetValue(value) as DataContext;
}

2 回复 | 直到 16 年前

Andrew Morton 4 年前

是-使用反射是确定查询所属DataContext的唯一方法。触发查询时创建的数据对象也是如此。

下面的内容并不能严格回答Rune的问题,但如果您想使用反射来确定数据对象是否附加到数据上下文并由其监视,则可能会有所帮助:

Private Const StandardChangeTrackerName As String = "System.Data.Linq.ChangeTracker+StandardChangeTracker"

Private _context As DataClasses1DataContext
Public Property Context() As DataClasses1DataContext
    Get
        Dim hasContext As Boolean = False
        Dim myType As Type = Me.GetType()
        Dim propertyChangingField As FieldInfo = myType.GetField("PropertyChangingEvent", BindingFlags.NonPublic Or BindingFlags.Instance)
        Dim propertyChangingDelegate As PropertyChangingEventHandler = propertyChangingField.GetValue(Me)
        Dim delegateType As Type = Nothing

        For Each thisDelegate In propertyChangingDelegate.GetInvocationList()
            delegateType = thisDelegate.Target.GetType()
            If delegateType.FullName.Equals(StandardChangeTrackerName) Then
                propertyChangingDelegate = thisDelegate
                hasContext = True
                Exit For
            End If
        Next

        If hasContext Then
            Dim targetField = propertyChangingDelegate.Target
            Dim servicesField As FieldInfo = targetField.GetType().GetField("services", BindingFlags.NonPublic Or BindingFlags.Instance)
            If servicesField IsNot Nothing Then

                Dim servicesObject = servicesField.GetValue(targetField)

                Dim contextField As FieldInfo = servicesObject.GetType.GetField("context", BindingFlags.NonPublic Or BindingFlags.Instance)

                _context = contextField.GetValue(servicesObject)

            End If
        End If
    
        Return _context
    End Get
    Set(ByVal value As DataClasses1DataContext)

        _context = value

    End Set

End Property

如果这有帮助,请在这篇文章上投票。

有关使用反射查找事件处理程序的详细信息:

Marc Gravell 16 年前