Question

我尝试在数据库服务器关闭时捕获数据库异常。我们使用Sybase IAnywhere。

我使用常规C＃try catch来获取数据库异常的名称。

try
{
//code here
}
catch (Exception ex)
{
Logging.Log.logItem(LogType.Exception, "Exception in isDBRunning", "App_Startup::isDBRunning() ", "GetBaseException=" + ex.GetBaseException().ToString() + "\nMessage=" + ex.Message + "\nStackTrace: " + ex.StackTrace + "\nInnerException: " + ex.InnerException);
}

打印出来的例外是：

GetBaseException=iAnywhere.Data.SQLAnywhere.SAException: Database server not found
   at iAnywhere.Data.SQLAnywhere.SAConnection.Open()
   at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure)
Message=The underlying provider failed on Open.
StackTrace:    at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure)
   at System.Data.EntityClient.EntityConnection.Open()
   at System.Data.Objects.ObjectContext.EnsureConnection()
   at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
   at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator()
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at System.Data.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__2[TResult](IEnumerable`1 sequence)
   at System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle[TResult](IEnumerable`1 query, Expression queryRoot)
   at System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute[S](Expression expression)
   at System.Linq.Queryable.Count[TSource](IQueryable`1 source)
   at Analogic.SystemSoftware.App.isDBRunning() in C:\workspace\SystemSoftware\SystemSoftware\src\startup\App.xaml.cs:line 158
InnerException: iAnywhere.Data.SQLAnywhere.SAException: Database server not found
   at iAnywhere.Data.SQLAnywhere.SAConnection.Open()
   at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure)

所以我认为iAnywhere.Data.SQLAnywhere.SAException是我应该处理的真正例外。然后我为它添加了一个捕获：

try
{
 //code here
}
catch (iAnywhere.Data.SQLAnywhere.SAException ex)
{
Logging.Log.logItem(LogType.Exception, "Exception in isDBRunning 1", "App_Startup::isDBRunning() ", "GetBaseException=" + ex.GetBaseException().ToString() + "\nMessage=" + ex.Message + "\nStackTrace: " + ex.StackTrace + "\nInnerException: " + ex.InnerException);
}

catch (Exception ex)
{
 Logging.Log.logItem(LogType.Exception, "Exception in isDBRunning", "App_Startup::isDBRunning() ", "GetBaseException=" + ex.GetBaseException().ToString() + "\nMessage=" + ex.Message + "\nStackTrace: " + ex.StackTrace + "\nInnerException: " + ex.InnerException);
}

但是没有发现iAnywhere.Data.SQLAnywhere.SAException。我仍然抓住了Exception。为什么呢？

Answer 1

Catch处理已抛出的实际异常的类型，而GetBaseException返回（第一个）InnerException（如果存在）。

打印出实际的异常以查看其特定类型（或在调试器中检查它，或者其他）然后捕获它。

Answer 2

因为抛出的东西不是SAException。尝试直接打印出异常而不是调用GetBaseException（）。

Answer 3

这不是SAException，这是内部异常。从堆栈跟踪中不清楚外部异常类型是什么。使用调试器或某些诊断代码很容易找到：

catch (Exception ex) {
    Console.WriteLine(ex.GetType().FullName;
    //...
}

Answer 4

检查您遇到的实际异常情况。您的GetBaseException()调用可能会掩盖正在发生的实际异常。

Answer 5

您可能需要执行以下操作：

try
{
    //code here
}
catch (Exception ex)
{
    if (ex.GetBaseException() is iAnywhere.Data.SQLAnywhere.SAException)
    {
        // log or handle known exception
    }
    else
    {
        // log unexpected exception
    } 
}

正如其他答案所述，如果您知道异常的实际类型，则可以通过将上述代码中的Exception更改为特定的特定类型来改进此。

为什么不能抓住内在的异常呢？

5 个答案: