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我正在开发一个从 Web 服务获取一些数据的应用程序。该程序是用 Xamarin Studio 用 C# 编写的。

该应用程序有一个存储在文件中的本地 SQLite 数据库。我创建了一个单独的 Database 类来简化数据库的内部工作（例如打开和关闭连接等）。这是此类的相关片段：

public static SqliteConnection connect(){
            string documentPath = System.Environment.GetFolderPath (System.Environment.SpecialFolder.Personal);
            try {
                return new SqliteConnection (string.Format ("Data Source={0};Version=3;", documentPath + "Database.db"));
            } catch {
                Console.WriteLine ("New DB created!");
                SqliteConnection.CreateFile (documentPath + "Database.db");
                return new SqliteConnection (string.Format ("Data Source={0};Version=3;", documentPath + "Database.db"));
            }
        }

public static void doQuery(string query){
            //Console.WriteLine ("Performing no-return query: " + query);
            using(var conn = connect()){
                conn.Open ();
                using(var cmd = conn.CreateCommand ()){
                    var trans = conn.BeginTransaction ();
                    cmd.CommandText = query;
                    cmd.CommandType = CommandType.Text;
                    cmd.Transaction = trans;
                    cmd.ExecuteNonQuery ();
                    trans.Commit ();
                }
            }
        }

public static DataTable getQueryResult(string query){
    //Console.WriteLine ("Performing return query: " + query);
    using (var conn = connect()) {
        conn.Open ();
        using (var cmd = conn.CreateCommand ()) {
            cmd.CommandText = query;
            cmd.CommandType = CommandType.Text;
            SqliteDataReader rdr = cmd.ExecuteReader ();
            DataTable dt = new DataTable ();
            dt.Load (rdr);
            return dt;
        }
    }
   }

大约执行后。1900 次查询，我收到此错误：

[mono] Unhandled Exception:
[mono] Mono.Data.Sqlite.SqliteException: Unable to open the database file
[mono] unable to open database file
[mono]   at Mono.Data.Sqlite.SQLite3.Reset (Mono.Data.Sqlite.SqliteStatement stmt) [0x00000] in <filename unknown>:0 
[mono]   at Mono.Data.Sqlite.SQLite3.Step (Mono.Data.Sqlite.SqliteStatement stmt) [0x00000] in <filename unknown>:0 
[mono]   at Mono.Data.Sqlite.SqliteDataReader.NextResult () [0x00000] in <filename unknown>:0 
[mono]   at Mono.Data.Sqlite.SqliteDataReader..ctor (Mono.Data.Sqlite.SqliteCommand cmd, CommandBehavior behave) [0x00000] in <filename unknown>:0 
[mono]   at (wrapper remoting-invoke-with-check) Mono.Data.Sqlite.SqliteDataReader:.ctor (Mono.Data.Sqlite.SqliteCommand,System.Data.CommandBehavior)
[mono]   at Mono.Data.Sqlite.SqliteCommand.ExecuteReader (CommandBehavior behavior) [0x00000] in <filename unknown>:0 
[mono]   at Mono.Data.Sqlite.SqliteCommand.ExecuteNonQuery () [0x00000] in <filename unknown>:0 
[mono]   at Mono.Data.Sqlite.SqliteTransaction..ctor (Mono.Data.Sqlite.SqliteConnection connection, Boolean deferred

在“var trans = conn.BeginTransaction();”处抛出此错误 doQuery 方法内的行。

我认为这与不处理对象有关，但由于我使用 using() 进行连接和命令，所以我不明白为什么......

我希望有一个人可以帮助我！

黛博尔

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2 回答 2

3

我解决了我的问题！在扩展应用程序的后台类中，我永久保持连接打开。现在插入一堆元素时我没有收到任何错误。

我希望这对其他人也有好处，因为我找不到有类似问题的人。

黛博尔

于 2013-08-06T08:28:57.780 回答
0

Wondering if you tried explicitely closing the connection for each time you open it. But using a singleton pattern using locks would be better as long as there is no concurrency issue. I'm very new to Xamarin but there probably is no connection caching.

于 2013-08-06T16:56:13.657 回答