我有一个例外。
我像这样为 InitializeComponent() 创建了一个 try catch。
try
{
InitializeComponent();
Auto_Complete();
}
catch(Exception ex)
{
System.Windows.Forms.MessageBox.Show(ex.Message);
}
然后我得到一个异常说“对象引用未设置为对象的实例。”。
我正在寻找错误的原因。
然后我发现错误是由于我在 xaml 中添加的控件引起的。
xmlns:wf="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
<WindowsFormsHost Margin="272,10,396,42" Width="240">
<wf:TextBox x:Name="txtAutoProductCode" AutoCompleteMode="SuggestAppend" AutoCompleteSource="CustomSource" />
</WindowsFormsHost>
这是我添加到 xaml 中以实现自动完成功能的 windows.forms 控件。
但是这个例外使它变得困难。
我创建了一个 autocomplete() 函数并连接了文本框：
void Auto_Complete()
{
txtAutoProductCode.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
txtAutoProductCode.AutoCompleteSource = AutoCompleteSource.CustomSource;
AutoCompleteStringCollection coll = new AutoCompleteStringCollection();
SqlCeCommand com = new SqlCeCommand("SELECT ProductCode FROM Category_Master(CategoryName)", con);
SqlCeDataReader dr;
try
{
dr = com.ExecuteReader();
while (dr.Read())
{
string aProduct = dr.GetString(0);
coll.Add(aProduct);
}
}
catch (Exception ex)
{
System.Windows.Forms.MessageBox.Show(ex.Message, System.Windows.Forms.Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error);
}
txtAutoProductCode.AutoCompleteCustomSource = coll;
}
public MainWindow()
{
try
{
InitializeComponent();
Auto_Complete();
}
catch(Exception ex)
{
System.Windows.Forms.MessageBox.Show(ex.ToString());
}
}
这是例外
System.Windows.Markup.XamlParseException was unhandled
HResult=-2146233087
Message='Initialization of 'Billing.MainWindow' threw an exception.' Line number '6' and line position '9'.
Source=PresentationFramework
LineNumber=6
LinePosition=9
StackTrace:
at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
at System.Windows.Application.LoadBamlStreamWithSyncInfo(Stream stream, ParserContext pc)
at System.Windows.Application.LoadComponent(Uri resourceLocator, Boolean bSkipJournaledProperties)
at System.Windows.Application.DoStartup()
at System.Windows.Application.<.ctor>b__1(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.ProcessQueue()
at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.Run()
at System.Windows.Application.RunDispatcher(Object ignore)
at System.Windows.Application.RunInternal(Window window)
at System.Windows.Application.Run(Window window)
at System.Windows.Application.Run()
at Billing.App.Main() in c:\Users\kamalmohan\Documents\Visual Studio 2012\Projects\Billing\Billing\obj\Debug\App.g.cs:line 0
at System.AppDomain._nExecuteAssembly(RuntimeAssembly 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.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException: System.InvalidOperationException
HResult=-2146233079
Message=Cannot have nested BeginInit calls on the same instance.
Source=PresentationFramework
StackTrace:
at System.Windows.FrameworkElement.BeginInit()
at MS.Internal.Xaml.Runtime.ClrObjectRuntime.InitializationGuard(XamlType xamlType, Object obj, Boolean begin)
InnerException: