使用实体框架重新创建已删除的数据库

Question

我正在尝试使用实体框架 CodeFirst 开发 Windows 窗体应用程序。在我删除数据库之前它工作得很好。试图重建它，但我收到此消息错误。没有对要从中创建数据库的类进行任何更改。我已经取出了用于数据库构建的类和代码 spippet（使用下面的上下文），并将它们放在另一个项目中，没有遇到任何问题。不过，在我的应用程序项目中，我得到了这个：

************** Exception Text **************
System.Data.Entity.Core.EntityCommandExecutionException: An error occurred while executing the command definition. See the inner exception for details. ---> System.Data.SqlClient.SqlException: Invalid column name 'Text'.
Invalid column name 'NumberOfCorrectAnswers'.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
   at System.Data.SqlClient.SqlDataReader.get_MetaData()
   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.<Reader>b__c(DbCommand t, DbCommandInterceptionContext`1 c)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.Reader(DbCommand command, DbCommandInterceptionContext interceptionContext)
   at System.Data.Entity.Internal.InterceptableDbCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)
   --- End of inner exception stack trace ---
   at System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)
   at System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context, ObjectParameterCollection parameterValues)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass3.<GetResults>b__2()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass3.<GetResults>b__1()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()
   at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at BD___TestingPlatform.AL.AL_Load(Object sender, EventArgs e) in d:\Cursuri\VS Projects\BD\Examen\BD - TestingPlatform\BD - TestingPlatform\AL.cs:line 98
   at System.Windows.Forms.Form.OnLoad(EventArgs e)
   at System.Windows.Forms.Form.OnCreateControl()
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl()
   at System.Windows.Forms.Control.WmShowWindow(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.ContainerControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmShowWindow(Message& m)
   at System.Windows.Forms.Form.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.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

我不得不提到我删除了迁移文件夹，试图从包控制台管理器中解决问题，但没有任何效果。通过查看创建它们的目录，我确保删除了初始数据库。我还从另一个示例应用程序中删除了数据库和迁移，重新创建时没有问题。

因为只有在您对其执行操作（例如，选择）时才会创建数据库，所以我有这个 sn-p，我正试图用它来触发进程。

using (TestingPlatformContext ctx = new TestingPlatformContext())
                {
                    //MessageBox.Show("Database created successfully");

                    var query = (from q in ctx.Questions    //line 98
                                 select q).ToList();
                    //{ QuestionID=q.QuestionID, Text=q.Text }).ToList();

                    if (query.Count == 0)
                        MessageBox.Show("No results");
                }

我的问题类如下：

public class Question
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int QuestionID { get; set; }

        public string Text { get; set; }
        public int NumberOfAnswers { get; set; }
        public int NumberOfCorrectAnswers { get; set; }

        public int PersonID { get; set; }
        public int SubjectID { get; set; }
        public virtual List<Answer> Answers { get; set; }
    }

P.S.：我使用的是 Visual Studio 2012，EntityFramework 6.1.1。

Answer 1

清理解决方案，并检查 web.config 中的数据库连接字符串。并检查您是否删除了正确的数据库。

另一方面，通过调用属性名称“文本”，我相信这是否会导致您出现问题或至少会导致混乱。像描述这样的名称更有可能是更好的选择。