C# 单声道+；SQLite。无法打开数据库

我有一个带有构造函数和方法的

DBHandler

类，用于更新SQLite数据库或向其中插入新记录：

public class DBHandler
    {
        private string dbName;
        private string tableName = "table1";
        private string dbPath;

        public DBHandler (string _dbName)
        {
            dbName = _dbName;
            dbPath = Path.Combine(Directory.GetCurrentDirectory (), dbName);

            bool exists = File.Exists (dbPath);
            if (!exists) {
                Mono.Data.Sqlite.SqliteConnection.CreateFile (dbPath);
                string createQuery = "CREATE TABLE " + tableName +
                                     "(" +
                                     "word1," +
                                     "word2," +
                                     "n INT INTEGER DEFAULT 1," +
                                     "PRIMARY KEY (word1, word2)" +
                                     ");";

                using (SqliteConnection connection = new SqliteConnection (String.Format ("Data Source={0};", dbPath))) {   
                    connection.Open ();
                    using (var c = connection.CreateCommand ()) {
                        c.CommandText = createQuery;
                        c.ExecuteNonQuery ();
                    }
                }
            }
        }

        public void InputToDb (WordPair pair)
        {
            string word1 = pair.word1;
            string word2 = pair.word2;
            int n = pair.n;
            int newN = 1;

            using (SqliteConnection connection = new SqliteConnection (String.Format ("Data Source={0};", dbPath))) {
                connection.Open ();

                using (var c1 = connection.CreateCommand ()) { 
                    c1.CommandText = "SELECT n from " + tableName + " WHERE word1 = '" + word1 + "' AND word2 = '" + word2 + "';";
                    var r = c1.ExecuteReader ();
                    r.Read ();
                    if (!r.HasRows)
                        newN = 1;
                    else
                        newN = int.Parse (r ["n"].ToString ()) + 1;
                } 
            }

            using (SqliteConnection connection = new SqliteConnection (String.Format ("Data Source={0};", dbPath))) {
                connection.Open ();
                using (var c2 = connection.CreateCommand ()) { 
                    string inputQuery = "INSERT OR REPLACE INTO " + tableName + " (word1, word2, n) " +
                                        "VALUES ('" + word1 + "', " +
                                        "'" + word2 + "', " +
                                        newN.ToString () +
                                        ");";
                    c2.CommandText = inputQuery;
                    c2.ExecuteNonQuery ();
                }
            }
        }
}  

该类的用途如下：

DBHandler dbh = new DBHandler ("database6.db3");
 for (int i = 0; i < buffer.Count-1; i++) {
    WordPair tempPair = new WordPair (buffer.Dequeue(), buffer.Peek(), 1);
    dbh.InputToDb (tempPair);
 }

DBHandler dbh=newdbhandler（“database6.db3”）；
对于（int i=0；i

（

buffer

只是一个字符串队列）

---

这通常在几次迭代（通常为8-10次）中都能正常工作，然后在string

c2.ExecuteNonQuery（）中出现“无法打开数据库”异常在
inputODB（…）
方法中。上次使用后，似乎有什么东西（连接或命令）没有正确处理，但我不知道哪里出了问题。
问题如下：

你应该用这个

using (var r = c1.ExecuteReader ()) {
    r.Read ();
    ...
}

而不仅仅是这个

var r = c1.ExecuteReader ());
r.Read ();
...

希望你不要成为简化教程的牺牲品。
可能是重复的否，那个家伙甚至一次都无法打开他的数据库。我的代码通常会执行几次，然后就崩溃了。