Sqlite数据库文件无法删除

问题描述：

VS2010 Setup工程卸载安装程序时，发生本地sqlite数据库文件无法删除。该卸载程序在完成卸载前读取了本地数据库的信息，代码大致如下：

private DataTable GetDataTableBySql(string databaseFilePath,string sql) { SQLiteConnection conn = new SQLiteConnection("Data Source=" + databaseFilePath+ ";Version=3"); DataTable datatable = new DataTable(); try { conn.Open(); SQLiteCommand comm = new SQLiteCommand(sql, conn); SQLiteDataReader reader = comm.ExecuteReader(); DataColumn column = new DataColumn(); for (int i = 0; i < columns.Count(); i++) { if (columns[i].Length > 0) { datatable.Columns.Add(columns[i].ToString()); } } while (reader.Read()) { DataRow dr = datatable.NewRow(); for (int i = 0; i < reader.FieldCount; i++) { dr[i] = reader[i].ToString(); } datatable.Rows.Add(dr); dr = null; } reader.Close(); conn.Close(); } catch (Exception ex) { conn.Close(); return datatable; } return datatable; }

数据库信息读取完毕后，也调用close()方法关闭了连接，但是无法完成程序的卸载过程，报“另一个应用程序已经以独占模式访问文件...”。

问题解决：

上述代码中，虽然已经调用close()方法，但是C#的垃圾回收机制并没有马上回收数据库连接对象。有两种办法可以解决上述问题。

其一，调用Dispose方法，让垃圾回收机制立即回收数据库连接对象。

private DataTable GetDataTableBySql(string databaseFilePath,string sql) { SQLiteConnection conn = new SQLiteConnection("Data Source=" + databaseFilePath+ ";Version=3"); DataTable datatable = new DataTable(); try { conn.Open(); SQLiteCommand comm = new SQLiteCommand(sql, conn); SQLiteDataReader reader = comm.ExecuteReader(); DataColumn column = new DataColumn(); for (int i = 0; i < columns.Count(); i++) { if (columns[i].Length > 0) { datatable.Columns.Add(columns[i].ToString()); } } while (reader.Read()) { DataRow dr = datatable.NewRow(); for (int i = 0; i < reader.FieldCount; i++) { dr[i] = reader[i].ToString(); } datatable.Rows.Add(dr); dr = null; } reader.Close(); //立即释放comm comm.Dispose(); conn.Close(); //立即释放conn conn.Dispose(); } catch (Exception ex) { conn.Close(); return datatable; } return datatable; }

其二，使用using(){}，using语句块中的对象，在语句块结束后会由马上被回收。

private DataTable GetDataTableBySql1(string databaseFilePath,string sql) { DataTable datatable = new DataTable(); try { using (SQLiteConnection conn = new SQLiteConnection("Data Source=" + databaseFilePath+ ";Version=3")) { conn.Open(); using (SQLiteCommand comm = new SQLiteCommand(sql, conn)) { using (SQLiteDataReader reader = comm.ExecuteReader()) { DataColumn column = new DataColumn(); for (int i = 0; i < columns.Count(); i++) { if (columns[i].Length > 0) { datatable.Columns.Add(columns[i].ToString()); } } while (reader.Read()) { DataRow dr = datatable.NewRow(); for (int i = 0; i < reader.FieldCount; i++) { dr[i] = reader[i].ToString(); } datatable.Rows.Add(dr); dr = null; } } } conn.Close(); } } catch (Exception ex) { return datatable; } return datatable; }