【发布时间】：2012-12-19 15:42:25
【问题描述】：
一些背景
我的 Asp.Net MVC 4 数据库第一个应用程序、提交和评论中有 2 个表。 （还有很多，但与这个问题无关）。任何给定的提交都可以关联任意数量的评论（一对多）。
我有一个提交详细信息页面，用户可以在该页面上打开一个带有部分视图的 jQuery 对话框，以便为提交添加评论。此部分视图绑定到为添加 cmets 而创建的强类型视图模型。
表格/模型
提交表
这是提交表的类模型。 （为简单起见，我省略了一些属性）。
Partial Public Class Submission
Public Property Submission_ID As Integer
Public Property Submission_Hash As String
Public Property Created As Nullable(Of Date)
Public Property Modified As Date
Public Overridable Property Comments As ICollection(Of Comment) = New HashSet(Of Comment)
End Class
评论表
这里是 Comment 表的类模型。 （同样，为简单起见，我省略了一些属性）。
Partial Public Class Comment
Public Property Comment_ID As Integer
Public Property User_ID As Nullable(Of Integer)
Public Property Comment_Type As Nullable(Of Integer)
Public Property Comment1 As String
Public Property Created As Nullable(Of Date)
Public Property Modified As Date
Public Overridable Property Comment_Type1 As Comment_Type
Public Overridable Property User As User
Public Overridable Property Submissions As ICollection(Of Submission) = New HashSet(Of Submission)
End Class
要求
我想要做的是向给定提交的已存在的 cmets 集合添加新评论。
到目前为止...
到目前为止，我有一个添加注释对话框的视图模型，它在我的控制器中初始化，然后将填充的视图模型返回给控制器的 post 方法。这是代码
视图模型
Public Class SubmissionAddCommentViewModel
<Display(Name:="Submission")> _
Public Property Submission_ID As Integer
<Display(Name:="User")> _
Public Property User_ID As Integer
<Display(Name:="Comment type")> _
Public Property Comment_Type As Integer
<Required(ErrorMessage:="Please enter a comment.")> _
<Display(Name:="Comment")> _
Public Property Comment As String
End Class
ViewModel 构建器
Public Class SubmissionAddCommentViewModel_Builder
Implements IModelBuilder(Of SubmissionAddCommentViewModel, Comment)
ReadOnly db As GeosightEntities
ReadOnly submission As Submission
Public Sub New(db As GeosightEntities, submission As Submission)
Me.db = db
Me.submission = submission
End Sub
Public Function CreateFrom(entity As Comment) As SubmissionAddCommentViewModel Implements IModelBuilder(Of SubmissionAddCommentViewModel, Comment).CreateFrom
Dim model = New SubmissionAddCommentViewModel()
model.Submission_ID = submission.Submission_ID
model.User_ID = GetLoggedIn_ID()
Return model
End Function
Public Function Rebuild(model As SubmissionAddCommentViewModel) As SubmissionAddCommentViewModel Implements IModelBuilder(Of SubmissionAddCommentViewModel, Comment).Rebuild
Return model
End Function
Public Sub Add(model As SubmissionAddCommentViewModel)
Dim comment As New Comment
' Map the ViewModel and Model fields
comment.Comment_Type1 = If(IsNothing(model.Comment_Type), Nothing, db.Comment_Type.Find(model.Comment_Type))
comment.User = db.Users.Find(model.User_ID)
comment.Comment1 = model.Comment
comment.Modified = Now
' Add the comment
db.Submissions.Find(model.Submission_ID).Comments.Add(comment)
db.SaveChanges()
End Sub
End Class
控制器获取方法
Function AddComment(Optional ByVal id As Integer = Nothing) As ActionResult
Dim commentAddView As New SubmissionAddCommentViewModel
Dim submission As Submission = db.Submissions.Find(id)
Dim comment As New Comment
If IsNothing(submission) Then
Return HttpNotFound()
End If
Me.builder_AddComment = New SubmissionAddCommentViewModel_Builder(db, submission)
' Create the instance of the submission add comment view model
commentAddView = builder_AddComment.CreateFrom(comment)
If Request.IsAjaxRequest Then
Return PartialView("AddCommentPartial", commentAddView)
End If
Return View(commentAddView)
End Function
Controller Post 方法
<HttpPost()> _
Function AddComment(ByVal commentAddView As SubmissionAddCommentViewModel) As ActionResult
Dim comment As New Comment
builder_AddComment = New SubmissionAddCommentViewModel_Builder(db, db.Submissions.Find(commentAddView.Submission_ID))
' Handle invalid comment models
If Not ModelState.IsValid Then
If Request.IsAjaxRequest Then
Return PartialView("AddCommentPartial", commentAddView)
End If
Return View(commentAddView)
End If
' Add the comment
Me.builder_AddComment.Add(commentAddView)
' Display the successful message
If Request.IsAjaxRequest Then
Return PartialView("AddCommentSuccessPartial", commentAddView)
End If
Return RedirectToAction("Details", New With {.id = commentAddView.Submission_ID})
End Function
问题
在测试上述功能时，在 ViewModel 构建器中一直执行到 db.SaveChanges() 是成功的，但是一旦运行此行，执行就会停止。我不知道发生了什么，结果完全卡住了。
有谁知道A)我要以正确的方式添加评论吗？ B) 为什么这一行在没有任何错误的情况下停止执行？
更新
感谢 Peter Smith 提出的在代码周围放置 Try Catch 的建议，我不知道为什么我一开始没有想到或这样做。
我现在收到以下错误：
{MySql.Data.MySqlClient.MySqlException (0x80004005)：您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册以获取正确的语法，以便在第 1 行的 '(SELECT" & vbLf & "
Submission_Comment.Submission_ID, " & vbLf & "Submission_Comment.' at line 1" & vbCrLf & 附近使用"在 MySql.Data.MySqlClient.MySqlStream.ReadPacket()" & vbCrLf & " 在 MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& affectedRow, Int64& insertedId)" & vbCrLf & " 在 MySql.Data.MySqlClient.Driver.GetResult （Int32 statementId，Int32& 影响行，Int64&insertedId）“& vbCrLf &”在 MySql.Data.MySqlClient.Driver.NextResult（Int32 statementId，布尔力）“& vbCrLf &“在 MySql.Data.MySqlClient.MySqlDataReader.NextResult()” & vbCrLf & " 在 MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior 行为)" & vbCrLf & " 在 MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()" & vbCrLf & " 在 MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery ()" & vbCrLf & " 在 MySql.Data.Entity.EFMySqlCommand.ExecuteNonQuery()" & vbCrLf & " 在 System.Data.Mapping.Update.In ternal.DynamicUpdateCommand.Execute(UpdateTranslator 转换器，EntityConnection 连接，Dictionary2 identifierValues, List1 generatedValues)" & vbCrLf & " at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter 适配器)}
【问题讨论】：
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尝试（原文如此）在您的 Add 方法中的 db 部分周围添加一个 try catch 块；这应该会为您提供有关错误的更多详细信息。
标签： asp.net-mvc model icollection