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为什么在保存数据库条目时收到“未处理的异常”？

2015-09-15 29 views
2

我目前正在研究一个数据库，用于跟踪停放在停车场的车辆。不过，我遇到了一些将新记录保存到数据库表的问题。现在我还是比较新的程序，所以我无法理解我收到的错误。我尝试过查找并找到类似的情况，但不完全一样。我已经在C＃中创建了应用程序，并且我的数据库是一个访问.mdb文件。为什么在保存数据库条目时收到“未处理的异常”？

的当前错误我收到如下：

“‘System.InvalidOperationException’类型的未处理的异常出现在system.data.dll

其他信息：不允许改变“的ConnectionString 'property.connection's current state is open“

我想指出，只有当我点击保存并且文本框中有值时才会发生这种情况。如果我点击保存而不输入任何内容，它会显示“访客信息已成功保存”。

我不知道发生了什么，所以我希望这里有人能够提供帮助。我已经为Call应用程序提供了我的应用程序的代码。

下面是我的应用程序的代码：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows; 
using System.Windows.Controls; 
using System.Windows.Data; 
using System.Windows.Documents; 
using System.Windows.Input; 
using System.Windows.Media; 
using System.Windows.Media.Imaging; 
using System.Windows.Navigation; 
using System.Windows.Shapes; 
using System.Data.OleDb; 
using System.Data; 
using System.ComponentModel; 


namespace ParkingDatabase 
{ 
/// <summary> 
/// Interaction logic for MainWindow.xaml 
/// </summary> 
public partial class MainWindow : Window 
{ 

    public MainWindow() 
    { 
     InitializeComponent(); 
    } 

    OleDbConnection DBConnect = new OleDbConnection(); 
    private void btnSave_Click(object sender, RoutedEventArgs e) 
    { 
     DBConnect.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\bkoso\Documents\Visual Studio 2015\Projects\ParkingDatabase\ParkingDatabase\ParkingData.mdb"; 
     DBConnect.Open(); 
     OleDbCommand com = new OleDbCommand("INSERT INTO Guest Info([Guest FName], [Guest LName], [Room #], Departure, Return, [Vehicle Colour], [Vehicle Make], [Plate #], [Contact FName], [Contact LName], [Contact #], [Contact Email], [Tag #]) Values(@[Guest FName], @[Guest LName], @[Room #], @Departure, @Return, @[Vehicle Colour], @[Vehicle Make], @[Plate #], @[Contact FName], @[Contact LName], @[Contact #], @[Contact Email], @[Tag #])", DBConnect); 
      com.Parameters.AddWithValue("@[Guest FName]", txtBxGstFName.Text); 
      com.Parameters.AddWithValue("@[Guest LName]", txtBxGstLName.Text); 
      com.Parameters.AddWithValue("@[Room #]", txtBxRm.Text); 
      com.Parameters.AddWithValue("@Departure", txtBxDDate.Text); 
      com.Parameters.AddWithValue("@[Return]", txtBxRDate.Text); 
      com.Parameters.AddWithValue("@[Vehicle Colour]", txtBxVColour.Text); 
      com.Parameters.AddWithValue("@[Vehicle Make]", txtBxVMake.Text); 
      com.Parameters.AddWithValue("@[Plate #]", txtBxPlate.Text); 
      com.Parameters.AddWithValue("@[Contact FName]", txtBxContactFName.Text); 
      com.Parameters.AddWithValue("@[Contact LName]", txtBxContactLName.Text); 
      com.Parameters.AddWithValue("@[Contact #]", txtBxPhone.Text); 
      com.Parameters.AddWithValue("@[Contact Email]", txtBxEmail.Text); 
      com.Parameters.AddWithValue("@[Tag #", txtBxTag.Text); 

     if (DBConnect.State == ConnectionState.Open) 
     { 
      try 
      { 
       //com.ExecuteNonQuery(); 
       MessageBox.Show("Guest Information Saved Successfully"); 
       txtBxGstFName.Text = ""; 
       txtBxGstLName.Text = ""; 
       txtBxRm.Text = ""; 
       txtBxDDate.Text = ""; 
       txtBxRDate.Text = ""; 
       txtBxVColour.Text = ""; 
       txtBxVMake.Text = ""; 
       txtBxPlate.Text = ""; 
       txtBxContactFName.Text = ""; 
       txtBxContactLName.Text = ""; 
       txtBxPhone.Text = ""; 
       txtBxEmail.Text = ""; 
       txtBxTag.Text = ""; 

      } 
      catch (Exception notSaved) 
      { 
       if (DBConnect != null && DBConnect.State != ConnectionState.Closed) 
       { 
        DBConnect.Close(); 
       } 
       MessageBox.Show("Error Saving Data \n" + notSaved.ToString()); 
       DBConnect.Close(); 
      } 
     } 
     else 
     { 
      MessageBox.Show("Connection Failed"); 
     } 
    } 

    private void btnClear_Click(object sender, RoutedEventArgs e) 
    { 

    } 

    private void btnView_Click(object sender, RoutedEventArgs e) 
    { 

    } 

    private void btnSame_Click(object sender, RoutedEventArgs e) 
    { 

    } 

    private void txtBoxGuestFirstName_TextChanged(object sender, TextChangedEventArgs e) 
    { 

    } 


} 
}

下面是调用堆栈：

> ParkingDatabase.exe!ParkingDatabase.MainWindow.btnSave_Click(object sender, System.Windows.RoutedEventArgs e) Line 36 C# 
PresentationCore.dll!System.Windows.RoutedEventHandlerInfo.InvokeHandler(object target, System.Windows.RoutedEventArgs routedEventArgs) Unknown 
PresentationCore.dll!System.Windows.EventRoute.InvokeHandlersImpl(object source, System.Windows.RoutedEventArgs args, bool reRaised) Unknown 
PresentationCore.dll!System.Windows.UIElement.RaiseEventImpl(System.Windows.DependencyObject sender, System.Windows.RoutedEventArgs args) Unknown 
PresentationCore.dll!System.Windows.UIElement.RaiseEvent(System.Windows.RoutedEventArgs e) Unknown 
PresentationFramework.dll!System.Windows.Controls.Primitives.ButtonBase.OnClick() Unknown 
PresentationFramework.dll!System.Windows.Controls.Button.OnClick() Unknown 
PresentationFramework.dll!System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(System.Windows.Input.MouseButtonEventArgs e) Unknown 
PresentationCore.dll!System.Windows.UIElement.OnMouseLeftButtonUpThunk(object sender, System.Windows.Input.MouseButtonEventArgs e) Unknown 
PresentationCore.dll!System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(System.Delegate genericHandler, object genericTarget) Unknown 
PresentationCore.dll!System.Windows.RoutedEventArgs.InvokeHandler(System.Delegate handler, object target) Unknown 
PresentationCore.dll!System.Windows.RoutedEventHandlerInfo.InvokeHandler(object target, System.Windows.RoutedEventArgs routedEventArgs) Unknown 
PresentationCore.dll!System.Windows.EventRoute.InvokeHandlersImpl(object source, System.Windows.RoutedEventArgs args, bool reRaised) Unknown 
PresentationCore.dll!System.Windows.UIElement.ReRaiseEventAs(System.Windows.DependencyObject sender, System.Windows.RoutedEventArgs args, System.Windows.RoutedEvent newEvent) Unknown 
PresentationCore.dll!System.Windows.UIElement.OnMouseUpThunk(object sender, System.Windows.Input.MouseButtonEventArgs e) Unknown 
PresentationCore.dll!System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(System.Delegate genericHandler, object genericTarget) Unknown 
PresentationCore.dll!System.Windows.RoutedEventArgs.InvokeHandler(System.Delegate handler, object target) Unknown 
PresentationCore.dll!System.Windows.RoutedEventHandlerInfo.InvokeHandler(object target, System.Windows.RoutedEventArgs routedEventArgs) Unknown 
PresentationCore.dll!System.Windows.EventRoute.InvokeHandlersImpl(object source, System.Windows.RoutedEventArgs args, bool reRaised) Unknown 
PresentationCore.dll!System.Windows.UIElement.RaiseEventImpl(System.Windows.DependencyObject sender, System.Windows.RoutedEventArgs args) Unknown 
PresentationCore.dll!System.Windows.UIElement.RaiseTrustedEvent(System.Windows.RoutedEventArgs args) Unknown 
PresentationCore.dll!System.Windows.UIElement.RaiseEvent(System.Windows.RoutedEventArgs args, bool trusted) Unknown 
PresentationCore.dll!System.Windows.Input.InputManager.ProcessStagingArea() Unknown 
PresentationCore.dll!System.Windows.Input.InputManager.ProcessInput(System.Windows.Input.InputEventArgs input) Unknown 
PresentationCore.dll!System.Windows.Input.InputProviderSite.ReportInput(System.Windows.Input.InputReport inputReport) Unknown 
PresentationCore.dll!System.Windows.Interop.HwndMouseInputProvider.ReportInput(System.IntPtr hwnd, System.Windows.Input.InputMode mode, int timestamp, System.Windows.Input.RawMouseActions actions, int x, int y, int wheel) Unknown 
PresentationCore.dll!System.Windows.Interop.HwndMouseInputProvider.FilterMessage(System.IntPtr hwnd, MS.Internal.Interop.WindowMessage msg, System.IntPtr wParam, System.IntPtr lParam, ref bool handled) Unknown 
PresentationCore.dll!System.Windows.Interop.HwndSource.InputFilterMessage(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam, ref bool handled) Unknown 
WindowsBase.dll!MS.Win32.HwndWrapper.WndProc(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam, ref bool handled) Unknown 
WindowsBase.dll!MS.Win32.HwndSubclass.DispatcherCallbackOperation(object o) Unknown 
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate callback, object args, int numArgs) Unknown 
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.TryCatchWhen(object source, System.Delegate callback, object args, int numArgs, System.Delegate catchHandler) Unknown 
WindowsBase.dll!System.Windows.Threading.Dispatcher.LegacyInvokeImpl(System.Windows.Threading.DispatcherPriority priority, System.TimeSpan timeout, System.Delegate method, object args, int numArgs) Unknown 
WindowsBase.dll!MS.Win32.HwndSubclass.SubclassWndProc(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam) Unknown 
[Native to Managed Transition] 
[Managed to Native Transition] 
WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame) Unknown 
WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) Unknown 
PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) Unknown 
PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) Unknown 
PresentationFramework.dll!System.Windows.Application.Run(System.Windows.Window window) Unknown 
PresentationFramework.dll!System.Windows.Application.Run() Unknown 
ParkingDatabase.exe!ParkingDatabase.App.Main() C# 
[Native to Managed Transition] 
[Managed to Native Transition] 
mscorlib.dll!System.AppDomain.ExecuteAssembly(string assemblyFile, System.Security.Policy.Evidence assemblySecurity, string[] args) Unknown 
Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() Unknown 
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) Unknown 
mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Unknown 
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Unknown 
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) Unknown 
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() Unknown

如果你想知道的未知调用堆栈是在语言栏。

在代码示例中，您可能会注意到第57行，com.ExecuteNonQuery（）; ，被评论了。这是因为我得到了一个语法错误。

任何帮助，这将不胜感激。如果我需要提供更多信息，请告诉我。

Bloodstalker

来源

2015-09-15 Bloodstalker

+1

您打开按钮点击连接，但不要将其关闭。无论如何，你应该真的把连接对象移动到方法中，然后在尝试修改打开的连接时不会遇到任何问题。代码中数据库的一般经验法则是：尽可能晚地连接，尽快断开连接。 – DavidG

+0

并使用* using *语句，因此您不能忘记关闭它。 –

+0

，如果抛出异常，你将在当前代码中关闭两次。一次，如果它没有关闭，并且在显示消息框之后不再是空的，并且如果它成功的话，你永远不会关闭连接。只要做一下hans所说的事，而忘记处理连接状态。 ....什么时候你真的执行命令？你不会得到一个语法错误，直到你执行它 –

回答

1

而且还有一个错字：

这样的：

com.Parameters.AddWithValue（ “@ [标签＃”，txtBxTag.Text）;

应该是：

com.Parameters.AddWithValue（ “@ [标记＃]”，txtBxTag.Text）;

来源

2015-09-15 11:09:51 Csab

+1

这不是一个答案，它应该是一个评论或编辑建议。 –

+0

感谢Csab真正解决了问题，并成功地向我提供了我期待的“访客信息保存成功”的消息。但是现在我可能会遇到一个新的错误，我需要解决大声笑。 – Bloodstalker

+1

还有一个错字：“INSERT INTO客户信息（”应该插入[Guest Info]（ – gd73

0

using声明会为您关闭连接。请查看MSDN的OleDbConnection大小写（跳转到本文末尾的“示例”部分）。

您的代码应该是这样的：

private void btnSave_Click(object sender, RoutedEventArgs e) 
{ 
    using (OleDbConnection DBConnect = new OleDbConnection()) 
    { 
     DBConnect.ConnectionString = @"Provider=Mi..."; 
     DBConnect.Open(); 
     OleDbCommand com = new OleDbCommand("INSERT INTO ...", DBConnect); 

     // Parameters goes here 

     if (DBConnect.State == ConnectionState.Open) 
     { 
      com.ExecuteNonQuery(); 
     } 

     //... 

     // No need to close connection 
    } 
}

来源

2015-09-15 11:13:41

+0

我想我明白了，但请改正我我错了，这是否意味着我应该将连接字符串设置为一个单独的类，并使用提到的语句调用该类？ – Bloodstalker

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