LINQ to SQL更新问题

Question

我正尝试使用LINQ to SQL更新我的Students表记录。问题是当对象的其中一个属性发生变化时，'PropertyChanging'使用'SendPropertyChanging（）'方法触发事件。

请注意：

1. student_id数据是PK
2. 数据类型匹配

这里是完全的ArgumentException：

GenericArguments [2]，“系统。字符串'，在 'System.Data.Linq.Mapping.PropertyAccessor + Accessor`3 [T，V，V2]' 违反了'V2'类型的约束。

堆栈strace的

在System.RuntimeType.ValidateGenericArguments（的MemberInfo 定义，RuntimeType [] genericArguments，例外五）在 System.RuntimeType.MakeGenericType在 系统（类型[]实例化）。 Data.Linq.Mapping.PropertyAccessor.Create（Type objectType， PropertyInfo pi，MetaAccessor storageAccessor）at System.Data.Linq.Mapping.AttributedMetaDataMember.MakeMemberAccessor（Type accessorType，MemberInfo mi，MetaAccessor storage）at 个System.Data.Linq.Mapping.AttributedMetaDataMember.InitAccessors（）
在 System.Data.Linq.Mapping.AttributedMetaDataMember.get_StorageAccessor（） 在 System.Data.Linq.ChangeTracker.StandardChangeTracker.StandardTrackedObject.CreateDataCopy（对象 实例）处 pro.Student.SendPropertyChanging（） System.Data.Linq.ChangeTracker.StandardChangeTracker.OnPropertyChanging（对象 发件人，PropertyChangingEventArgs参数）在 C：\的Inetpub \ wwwroot的\亲\模型\ Student.vb：线384 at pro.Student.set_first_name（String value）in C：\ inetpub \ wwwroot \ pro \ Models \ Student.vb：line 132 at pro .WizardController.SetLanguageAndText（LanguageAndTextInfo ltInfo） C：\ inetpub \ wwwroot \ pro \ Controllers \ WizardController.vb：line 517 at lambda_method（Closure，ControllerBase，Object []）at System.Web.Mvc.ActionMethodDispatcher.Execute在 System.Web.Mvc.ReflectedActionDescriptor.Execute（ControllerBase 控制器，对象[]参数）（ControllerContext controllerContext，IDictionary的参数）在 System.Web.Mvc.ControllerActionInvoker。 <> C_ DisplayClass15.b _12（） 在 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter（IActionFilter 滤波器，ActionExecutingContext preContext，Func`1续）

这里是学生。VB类：

Imports Microsoft.VisualBasic 
Imports System.Xml.Serialization 
Imports System.IO 
Imports System.Data.Linq.Mapping 
Imports System.ComponentModel 

<Global.System.Data.Linq.Mapping.TableAttribute(name:="dbo.Students")> _ 
Public Class Student 
    Implements System.ComponentModel.INotifyPropertyChanging, System.ComponentModel.INotifyPropertyChanged 

    Private Shared emptyChangingEventArgs As PropertyChangingEventArgs = New PropertyChangingEventArgs(String.Empty) 
    Private _student_id As System.Guid 
    Private _first_name As String 
    Private _last_name As String 
    Private _email As String 

    Public Sub New() 

    End Sub 


#Region "Properties" 
    <Global.System.Data.Linq.Mapping.ColumnAttribute(name:="student_id", Storage:="_student_id", DbType:="uniqueidentifier NOT NULL", IsPrimaryKey:=True, IsDbGenerated:=True, CanBeNull:=False)> _ 
    Public Property student_id() As System.Guid 
     Get 
      Return _student_id 
     End Get 
     Set(value As System.Guid) 
      If ((_student_id = value) = False) Then 
       SendPropertyChanging() 
       _student_id = value 
       SendPropertyChanged("student_id") 
      End If 
     End Set 
    End Property 

    <Global.System.Data.Linq.Mapping.ColumnAttribute(name:="first_name", Storage:="_first_name", DbType:="nvarchar(250) NOT NULL", CanBeNull:=False)> _ 
    Public Property first_name() As String 
     Get 
      Return _first_name 
     End Get 
     Set(ByVal value As String) 
      If ((_first_name = value) = False) Then 
       **SendPropertyChanging()** 
       _first_name = value 
       SendPropertyChanged("first_name") 
      End If 
     End Set 
    End Property 

    <Global.System.Data.Linq.Mapping.ColumnAttribute(name:="last_name", Storage:="_last_name", DbType:="nvarchar(250) NOT NULL", CanBeNull:=False)> _ 
    Public Property language() As String 
     Get 
      Return _last_name 
     End Get 
     Set(ByVal value As String) 
      If ((_last_name = value) = False) Then 
       **SendPropertyChanging()** 
       _last_name = value 
       SendPropertyChanged("last_name") 
      End If 
     End Set 
    End Property 

    <Global.System.Data.Linq.Mapping.ColumnAttribute(name:="email", Storage:="_email", DbType:="nvarchar(250) NOT NULL", CanBeNull:=False)> _ 
    Public Property email() As String 
     Get 
      Return _email 
     End Get 
     Set(ByVal value As String) 
      If ((_email = value) = False) Then 
       **SendPropertyChanging()** 
       _email = value 
       SendPropertyChanged("email") 
      End If 
     End Set 
    End Property 
#End Region 

#Region "Linq Methods" 
    Public Event PropertyChanging As PropertyChangingEventHandler Implements System.ComponentModel.INotifyPropertyChanging.PropertyChanging 
    Public Event PropertyChanged As PropertyChangedEventHandler Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged 

    Protected Overridable Sub SendPropertyChanging() 
     If ((Me.PropertyChangingEvent Is Nothing) = False) Then 
      RaiseEvent PropertyChanging(Me, emptyChangingEventArgs) 
     End If 
    End Sub 

    Protected Overridable Sub SendPropertyChanged(ByVal propertyName As [String]) 
     If ((Me.PropertyChangedEvent Is Nothing) = False) Then 
      RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName)) 
     End If 
    End Sub 
#End Region 
End Class 

这是我正在努力更新学生

Using context As New dbStudents(strConnString) 

    Dim tmpStudent = (From p In context.Students 
      Where p.student_id = CurStudent.student_id 
      Select p).FirstOrDefault() 

    tmpStudent.FirstName = CurStudent.FirstName 
    tmpStudent.LastName = CurStudent.LastName 
    tmpStudent.Email = CurStudent.Email 

    context.SubmitChanges() 

End Using 

谢谢！

Answer 1

正如我从堆栈跟踪调用SendPropertyChanging导致System.Data.Linq.ChangeTracker.StandardChangeTracker.OnPropertyChanging触发，其调用get存取器相同的属性，以便更改之前获取属性的数据副本。但是，您正在使用String.Empty作为属性名称，所以我的猜测是它无法通过名称找到属性。

尝试通过添加属性名称来更改方法SendPropertyChanging，就像使用SendPropertyChanged一样。