SqlCeDataReader始终为空

Question

嘿，伙计们我正在使用Windows Mobile 5.0（.Net 2.0） ，并且我陷入了一个小问题，我的阅读器始终为空。我的联系很好，我相信其他一切都很好，唯一的问题是读者。 在我的异常俘获它说

((System.Data.SqlServerCe.SqlCeException)(e)) : {"The operation completed successfully."} 
InnerException: Could not evaluate expression 

我的数据库文件未损坏我打开它的应用程序之外，一切都看起来很好。 我的代码如下：

public static List<Image> GetAll(BOI caller) 
    { 
     List<Image> images = new List<Image>(); 
     SqlCeConnection c = Connection.GetConnection(caller.ConnectionString); 

     if (c != null) 
     { 
      SqlCeCommand command = new SqlCeCommand("SELECT * FROM Images", c); 

      SqlCeDataReader reader = null; 
      try 
      { 
       reader = command.ExecuteReader(); <<<<< reader is null <<<<<<< 
      } 
      catch (Exception e) 
      { 
       while (reader != null && reader.Read()) 
       { 
        Image temp = new Image((int)reader["imageKey"], 
           (String)reader["filename"], 
           (byte[])reader["image"], 
           (reader["labelKey"] == DBNull.Value ? null : (int?)reader["labelKey"]), 
           (int)reader["priority"]); 
        temp.SetDBName(caller.ConnectionString); 

        images.Add(temp); 
       } 
      } 
     } 

     return images; 
    } 

编辑 我打开我的Connection.GetConnection连接（..）;

编辑：2 的e.StackTrace：

at System.Data.SqlServerCe.SqlCeDataReader.ProcessResults(Int32 hr) 
    at System.Data.SqlServerCe.SqlCeDataReader.FillMetaData(SqlCeCommand command) 
    at System.Data.SqlServerCe.SqlCeCommand.InitializeDataReader(SqlCeDataReader reader, Int32 resultType) 
    at System.Data.SqlServerCe.SqlCeCommand.ExecuteCommand(CommandBehavior behavior, String method, ResultSetOptions options) 
    at System.Data.SqlServerCe.SqlCeCommand.ExecuteReader(CommandBehavior behavior) 
    at System.Data.SqlServerCe.SqlCeCommand.ExecuteReader() 
    at Oralys.BOI.DataAccess.ImageMapper.GetAll(BOI caller) 
    at Oralys.BOI.BOI.get_Images() 
    at Oralys.BOI.BOI_Controller.FetchAllImages() 
    at IdeoVoiceMobile.RunProfile.InitBOI() 
    at IdeoVoiceMobile.RunProfile..ctor() 
    at IdeoVoiceMobile.Program.startProfile() 
    at IdeoVoiceMobile.Program.Main() 

获取连接函数：

public static SqlCeConnection GetConnection(string connectionString) 
    { 
     SqlCeConnection conn = null; 
     try 
     { 
      if (connections.Count == 0) 
      { 
       OpenConnection(connectionString); 
      } 
      conn = connections[connectionString]; 
     } 
     catch (System.Exception) 
     { 
     } 
     return conn; 
    } 

编辑：3 异常代码使用时

SqlCeCommand command = new SqlCeCommand("SELECT * FROM Images Where imageKey=6", c);

ExceptionCode: 0xc0000005 
ExceptionAddress: 0x0115438c 
Reading: 0x00000000 
Faulting module: sqlceqp35.dll 
Offset: 0x0001438c 

    at NativeMethods.GetKeyInfo(IntPtr pIUnknown, IntPtr pTx, String pwszBaseTable, IntPtr prgDbKeyInfo, Int32 cDbKeyInfo, IntPtr pError) 
    at SqlCeDataReader.FillMetaData(SqlCeCommand command) 
    at SqlCeCommand.InitializeDataReader(SqlCeDataReader reader, Int32 resultType) 
    at SqlCeCommand.ExecuteCommand(CommandBehavior behavior, String method, ResultSetOptions options) 
    at SqlCeCommand.ExecuteReader(CommandBehavior behavior) 
    at SqlCeCommand.ExecuteReader() 
    at ImageMapper.GetAll(BOI caller) 
    at BOI.get_Images() 
    at BOI_Controller.FetchAllImages() 
    at RunProfile.InitBOI() 
    at RunProfile..ctor() 
    at Program.startProfile() 
    at Program.Main() 

Answer 1

问题结束了，因为我使用System.Data.SqlServerCe 3.5.1.0当我切换到3.5.0.0它工作没有任何错误。 我把while循环放在catch语句之外。

但我仍然从MS恼怒，因为他们没有显示任何错误！

Answer 2

你永远不会打下面的代码行，除非cm.executereader抛出一个异常：

while (reader != null && reader.Read()) 

尝试将下面的代码catch语句

  while (reader != null && reader.Read()) 
      { 
       Image temp = new Image((int)reader["imageKey"], 
          (String)reader["filename"], 
          (byte[])reader["image"], 
          (reader["labelKey"] == DBNull.Value ? null : (int?)reader["labelKey"]), 
          (int)reader["priority"]); 
       temp.SetDBName(caller.ConnectionString); 

       images.Add(temp); 
      } 

Answer 3

Raym0nd之外，我猜猜你是新来的。

看看你提供的这个版本。

public static List<Image> GetAll(BOI caller) { 
    List<Image> images = new List<Image>(); 
    using (SqlCeCommand cmd = new SqlCeCommand("SELECT * FROM Images", Connection.GetConnection(caller.ConnectionString))) { 
    try { 
     cmd.Connection.Open(); 
     using (SqlCeReader reader = cmd.ExecuteReader()) { 
     while (reader.Read()) { 
      object imageKey = reader["imageKey"]; 
      object filename = reader["filename"]; 
      object image = reader["image"]; 
      object labelKey = reader["labelKey"]; 
      object priority = reader["priority"]; 
      Image img = new Image((interface)imageKey, (string)filename, (byte[])image, (int?)labelKey, (int)priority); 
      img.SetDBName(caller.ConnectionString); 
      images.Add(img); 
     } 
     } 
    } catch (SqlCeException err) { 
     Console.WriteLine(err.Message); 
     throw err; 
    } finally { 
     cmd.Connection.Close(); 
    } 
    } 
    return images; 
} 

你要添加一些功能在你的空整数的情况下，以测试你的对象，但大部分是干净和简单。

在Console.WriteLine()上划一个断点，如果发生异常，则将鼠标悬停在Message上。