Question

我有一个简单的表，其中包含主键（Identity）和少量varchar类型的列。我尝试使用以下语法删除/销毁具有给定主键的记录：

SS3Test.DAL.TestClass.Destroy(x => x.TestId == _testId);

但是当它被调用时，我得到以下异常：

Failed to convert parameter value from a Func`2 to a Int32.

堆栈跟踪如下：

System.InvalidOperationException was unhandled
  Message="Failed to convert parameter value from a Func`2 to a Int32."
  Source="SubSonic.Core"
  StackTrace:
       at SubSonic.Query.SqlQuery.Execute()
       at SubSonic.Repository.SubSonicRepository`1.Delete(Object key, IDataProvider provider)
       at SubSonic.Repository.SubSonicRepository`1.Delete(Object key)
       at SS3Test.DAL.TestClass.Destroy(Func`2 expression) in E:\temp\SS3TEst\SS3Test.DAL\ActiveRecord.cs:line 2149
       at SS3Test.Model.TestClass.Delete(Int32 warrantyId, Boolean destroy) in E:\temp\SS3TEst\SS3Test.Model\TestClass.cs:line 84
       at SS3Test.GUI.FrmTestClass.btnDelete_Click(Object sender, EventArgs e) in E:\temp\SS3TEst\SS3Test.GUI\FrmTestClass.cs:line 72
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at SS3Test.GUI.Program.Main() in E:\temp\SS3TEst\SS3Test.GUI\Program.cs:line 21
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: System.InvalidCastException
       Message="Failed to convert parameter value from a Func`2 to a Int32."
       Source="System.Data"
       StackTrace:
            at System.Data.SqlClient.SqlParameter.CoerceValue(Object value, MetaType destinationType)
            at System.Data.SqlClient.SqlParameter.GetCoercedValue()
            at System.Data.SqlClient.SqlParameter.Validate(Int32 index, Boolean isCommandProc)
            at System.Data.SqlClient.SqlCommand.BuildParamList(TdsParser parser, SqlParameterCollection parameters)
            at System.Data.SqlClient.SqlCommand.BuildExecuteSql(CommandBehavior behavior, String commandText, SqlParameterCollection parameters, _SqlRPC& rpc)
            at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
            at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
            at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
            at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
            at SubSonic.DataProviders.DbDataProvider.ExecuteQuery(QueryCommand qry)
            at SubSonic.Query.SqlQuery.Execute()
       InnerException: System.InvalidCastException
            Message="Object must implement IConvertible."
            Source="mscorlib"
            StackTrace:
                 at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
                 at System.Data.SqlClient.SqlParameter.CoerceValue(Object value, MetaType destinationType)

PS： - 我从这个答案得到了一个解决方法，即从db获取具有给定键的对象，然后在其上调用delete。它有效，但我想知道为什么我得到这个例外。我也在使用SS 3.0.3（今天下载（26Jan2K10））。

Answer 1

我不熟悉库或函数，但错误消息暗示您将函数作为参数传递，其中需要Int32。事实上，您将lambda函数（“=＆gt;”）作为参数传递给Destroy。所以要检查的第一件事是Destroy是否真的想要一个函数或整数。

如果不是这样，请注意lambda函数重新调整bool（==比较的结果），但错误意味着需要Int32。您可能必须将bool转换为int，您可以使用？：运算符轻松地将其转换为：

x => ((x.TestId == _testId) ? 1 : 0)

但当然，两个答案都取决于Destroy参数实际期望的内容。

Answer 2

它看起来像一个正确的错误，因为ActiveRecord Destroy方法所依赖的SubSonicRepository没有Delete(expression)重载。

我想如果你进入你的ActiveRecord.tt模板文件并找到：

    public static void Destroy(Func<<#=tbl.ClassName#>, bool> expression) {
        var repo = GetRepo();
        repo.Delete(expression);
    }

并将Delete替换为DeleteMany，这将删除为给定表达式返回true的所有记录（如果您使用的是主键，则希望只删除该记录：）

GC

Subsonic 3 ActiveRecord删除/销毁抛出奇怪的异常

2 个答案: