C# MySQL示例：Command.ExecuteReader引发异常

Question

我正在编写一段C#代码，从mysql数据库获取一些数据。我已经使用现成的示例开始了，但在rdr = cmd.ExecuteReader()处出现错误。

下面还显示了抛出异常的屏幕截图：

using System;
using MySql.Data.MySqlClient; 

public class Program
{

    static void Main() 
    {
            string serverName = "192.168.0.012";
            string port = "1234";
            string db = "cust_db";
            string userID = "root";
            string password = "pass";
            string cs = "Server=" + serverName + ";Port=" + port + ";Database=" + db + ";Uid=" + userID + ";password=" + password;


        MySqlConnection conn = null;
        MySqlDataReader rdr = null;

        try 
        {
            conn = new MySqlConnection(cs);
            conn.Open();

            string stm = "SELECT * FROM cust_tb";
            MySqlCommand cmd = new MySqlCommand(stm, conn);
            rdr = cmd.ExecuteReader();

            while (rdr.Read()) 
            {
                Console.WriteLine(rdr.GetInt32(0) + ": " 
                    + rdr.GetString(1));
            }

        } catch (MySqlException ex) 
        {
            Console.WriteLine("Error: {0}",  ex.ToString());

        } finally 
        {
            if (rdr != null) 
            {
                rdr.Close();
            }

            if (conn != null) 
            {
                conn.Close();
            }

        }
    }
}


at MySql.Data.MySqlClient.CharSetMap.GetChararcterSet(DBVersion version, String CharSetName)
   at MySql.Data.MySqlClient.NativeDriver.GetFieldMetaData41()
   at MySql.Data.MySqlClient.NativeDriver.GetFieldMetaData()
   at MySql.Data.MySqlClient.NativeDriver.ReadColumnMetadata(Int32 count)
   at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
   at Program.Main() in c:\Users\omran.alhammadi\Desktop\csMysqlConnection\csMysqlConnection\Program.cs:line 28
   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()</StackTrace><ExceptionString>System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at MySql.Data.MySqlClient.CharSetMap.GetChararcterSet(DBVersion version, String CharSetName)
   at MySql.Data.MySqlClient.NativeDriver.GetFieldMetaData41()
   at MySql.Data.MySqlClient.NativeDriver.GetFieldMetaData()
   at MySql.Data.MySqlClient.NativeDriver.ReadColumnMetadata(Int32 count)
   at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
   at Program.Main() in c:\Users\omran.alhammadi\Desktop\csMysqlConnection\csMysqlConnection\Program.cs:line 28
   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()</ExceptionString></Exception></TraceRecord>
An unhandled exception of type 'System.Collections.Generic.KeyNotFoundException' occurred in mscorlib.dll
Additional information: The given key was not present in the dictionary.
The program '[17084] csMysqlConnection.vshost.exe: Managed (v4.0.30319)' has exited with code -1 (0xffffffff).

- Omran

---

异常抛出在哪一行？ - Joel Coehoorn

在此处，rdr = cmd.ExecuteReader() - Omran

你能展示更多的异常细节吗，比如堆栈跟踪信息？ - Dylan Smith

我编辑了帖子以显示堆栈跟踪。 - Omran

这里有一个类似的帖子链接。你可以在那里找到解决方案。 - user1878182

这个问题是与VS 2012还是MySQL数据库有关？ - Omran

Answer 1

我一直遇到这个问题，做了一些研究。过了一会儿，我终于解决了这个问题。

我的问题是数据库表编码的问题。我原来使用的是 utf32_unicode_ci，现在改成了 utf8_unicode_ci。现在它完美地工作了。

希望你也能成功解决此类问题。

- Willy Wonka