【发布时间】：2019-01-01 19:02:56
【问题描述】：
我有一个类来处理客户端和数据库 (MySQL) 之间的所有数据库交互（我知道并理解我不应该允许直接访问数据库）
public T getDatabaseValue<T>(string value, string query)
{
try
{
connection = new MySqlConnection(connectionString);
connection.Open();
command = new MySqlCommand(query, connection);
MySqlDataReader reader = command.ExecuteReader();
if (reader.Read())
{
return (T)reader[value];
}
else
return default(T);
}
catch (MySqlException SQLex)
{
Debug.Log("Database get failed (SQL Exception), query: " + query);
Debug.Log("Exception Message: " + SQLex.Message);
return default(T);
}
catch (System.Exception ex)
{
Debug.Log("Database get failed (System Exception), query: " + query);
Debug.Log("Exception Message: " + ex.Message);
return default(T);
}
}
这在编辑器中完美运行。在 Android 上构建和运行时，我通过 Monitor 收到此错误消息：
01-01 15:21:14.141: I/Unity(23761): (Filename: ./Runtime/Export/Debug.bindings.h Line: 43)
01-01 15:21:14.829: I/Unity(23761): Database get failed (System Exception), query: SELECT MAX(DT_Stamp) FROM tbl_Store;
01-01 15:21:14.829: I/Unity(23761):
01-01 15:21:14.829: I/Unity(23761): (Filename: ./Runtime/Export/Debug.bindings.h Line: 43)
01-01 15:21:14.829: I/Unity(23761): Exception Message: Index was outside the bounds of the array.
我没有使用数组来存储阅读器的内容，这是调用此示例的行（它发生在所有数据库交互中，不仅仅是这个，而且不仅仅是这个数据库查询函数）：
DateTime DB_Date = getDatabaseValue<DateTime>("MAX(DT_Stamp)", "SELECT MAX(DT_Stamp) FROM tbl_Store;");
这是 tbl_Store 的内容：
(Item_ID (int)), (Item_Name (varchar)), (Item_Price (float)), (In_Use (bit)), (DT_Stamp (datetime))
4 Hero Upgrade #1 100 1 2018-12-11 09:53:14
5 Hero Upgrade #2 300 1 2018-12-11 09:53:14
6 Hero Upgrade #3 700 1 2018-12-11 09:53:14
我还在一个更基本的项目中尝试过，以获取 Android 返回的核心错误消息：
01-01 17:23:48.307: E/Unity(10476): IndexOutOfRangeException: Index was outside the bounds of the array.
01-01 17:23:48.307: E/Unity(10476): at System.Diagnostics.TraceInternal.get_AppName () [0x0000e] in <ac210d81537245bc838518cc8e845861>:0
01-01 17:23:48.307: E/Unity(10476): at System.Diagnostics.TraceInternal.TraceEvent (System.Diagnostics.TraceEventType eventType, System.Int32 id, System.String format, System.Object[] args) [0x0003d] in <ac210d81537245bc838518cc8e845861>:0
01-01 17:23:48.307: E/Unity(10476): at System.Diagnostics.Trace.TraceError (System.String message) [0x00000] in <ac210d81537245bc838518cc8e845861>:0
01-01 17:23:48.307: E/Unity(10476): at MySql.Data.MySqlClient.MySqlTrace.LogError (System.Int32 id, System.String msg) [0x00028] in <326e9aab93854e739606c3572c385a34>:0
01-01 17:23:48.307: E/Unity(10476): at MySql.Data.MySqlClient.MySqlPool.TryToGetDriver () [0x00031] in <326e9aab93854e739606c3572c385a34>:0
01-01 17:23:48.307: E/Unity(10476): at MySql.Data.MySqlClient.MySqlPool.GetConnection () [0x0001c] in <326e9aab93854e739606c3572c385a34>:0
01-01 17:23:48.307: E/Unity(10476): at MySql.Data.MySqlClient.MySqlConnection.Open () [0x000f3] in <326e9aab93854e739606c3572c385a34>:0
01-01 17:23:48.307: E/Unity(10476): at texttest1.Start () [0x00011] in <dd75ac8e3f854a97ac132dae6ec658fd>:0
我可能在这里遗漏了一些非常简单的东西，但我们将不胜感激！
【问题讨论】：
-
getDatabaseValue<DateTime>("dt_stamp", "SELECT MAX(DT_Stamp) dt_stamp FROM tbl_Store;")也会失败吗？ -
嘿，是的，所以我用于“更简单”版本的代码如下：` void Start () { connection = new MySqlConnection(connectionString);连接.打开（）； command = new MySqlCommand("SELECT Item_Name FROM tbl_Store;", connection); MySqlDataReader reader = command.ExecuteReader(); text = GameObject.Find("Text").GetComponent
();阅读器.Read(); text.text = reader["Item_Name"].ToString(); }` -
实际上并没有使用相同的查询，它仍然在 Monitor.bat 中产生相同的结果
标签： c# mysql .net visual-studio unity3d