问题描述

我在我的应用程序中使用 SQLite 作为数据库引擎，但同时应用程序必须是跨平台的，所以我决定使用 Mono.Data.Sqlite.这就是我所做的:

• 安装最新版本的 Mono (4.0.2 SR 2)，将 Mono.Data.Sqlite.dll 从 Mono 的目录 (net4_5) 复制到我在 Visual Studio 2015 中的项目中

• 已下载并复制预编译的 sqlite3.dll 库.

然后我写了一个简单的应用程序:

 const string databaseFileName = "somedata.db";var path = Directory.GetCurrentDirectory() + Path.DirectorySeparatorChar + databaseFileName;if (!File.Exists(path)) SqliteConnection.CreateFile(databaseFileName);var connString = string.Format("Data Source=file:{0}", databaseFileName);使用 (var conn = new SqliteConnection(connString)){conn.Open();/* 一些代码 */conn.ChangePassword("testpassword");conn.Close();}

但我面临一些问题:

• 首先，当我在连接字符串中使用 Data Source=file:{0} 时，会引发异常:不支持 URI 格式".将其替换为 URI=file:{0} 会有所帮助，但为什么第一个选项不起作用?

• 其次，当我调用 conn.ChangePassword("testpassword") 时会抛出异常:System.EntryPointNotFoundException: Unable to find an entry point named "sqlite3_rekey" in DLL "sqlite3"

• 第三，对已经加密的数据库使用URI=file:{0};Password=testpassword会抛出异常:System.EntryPointNotFoundException: Unable to find an entry point named "sqlite3_key"在 DLL sqlite3"中

SQLite 的官方包装器实际上不会发生这种情况，但 Mono 会发生这种情况.

附:当我不使用加密和 Data Source=file:{0} 而不是 URI=file:{0}

#if !PLATFORM_COMPACTFRAMEWORK[DllImport(SQLITE_DLL, CallingConvention = CallingConvention.Cdecl)]#别的[DllImport(SQLITE_DLL)]#万一内部静态外部 int sqlite3_key(IntPtr db, byte[] key, int keylen);

#if !PLATFORM_COMPACTFRAMEWORK[DllImport(SQLITE_DLL, CallingConvention = CallingConvention.Cdecl)]#别的[DllImport(SQLITE_DLL)]#万一内部静态外部 int sqlite3_rekey(IntPtr db, byte[] key, int keylen);

<代码>...SQLITE_API int SQLITE_STDCALL sqlite3_rekey...SQLITE_API int SQLITE_STDCALL sqlite3_key...

I'm using SQLite as database engine in my app, but at the same time the application must be cross-platform, so i have decided to use Mono.Data.Sqlite. And this what i did:

• Installed the latest version of Mono (4.0.2 SR 2), copied Mono.Data.Sqlite.dll from Mono's directory (net4_5) to my project in Visual Studio 2015

• Downloaded and copied precompiled sqlite3.dll library.

And then i wrote a simple app:

        const string databaseFileName = "somedata.db";
        var path = Directory.GetCurrentDirectory() + Path.DirectorySeparatorChar + databaseFileName;

        if (!File.Exists(path)) SqliteConnection.CreateFile(databaseFileName);

        var connString = string.Format("Data Source=file:{0}", databaseFileName);

        using (var conn = new SqliteConnection(connString))
        {
            conn.Open();

            /* Some code */
            conn.ChangePassword("testpassword");
            conn.Close();
        }

But i'm facing with some issues:

• First, when i'm using Data Source=file:{0} in connection string, it throws an exception: "URI formats are not supported". Replacing it to URI=file:{0} helps, but why the first option doesn't work?

• Second, when i call conn.ChangePassword("testpassword") it throws an exception: System.EntryPointNotFoundException: Unable to find an entry point named "sqlite3_rekey" in DLL "sqlite3"

• Third, using URI=file:{0};Password=testpassword with the already encrypted database throws an exception: System.EntryPointNotFoundException: Unable to find an entry point named "sqlite3_key" in DLL "sqlite3"

It doesn't actually happen with official wrapper for SQLite, but happens with Mono's.

P.S. Mono's wrapper works normally when i don't use encryption and Data Source=file:{0} instead of URI=file:{0}

P.S.S. Windows 10, Visual Studio 2015 + latest version of Mono and SQLite

For the first issue, convert your URI to a local file path; new Uri(databaseFileURI).LocalPath. The file:// or file: is not used by Sqlite and stripped by the C# helper code, see the code in "Mono.Data.Sqlite_2.0/SQLiteConnection.cs".

For the second/third issues:

The sqlite3 native lib that you have appears to not match the Mono's dll import statements, you can use bindump /EXPORTS to confirm this. The Mono DllImports and the matching SQLite .h exports follows:

NOTE: This of course assumes you are have the correct ARCH for the native dll and you are not compiling a Uni-app in Windows.

Grep'ing out the source of "Mono.Data.Sqlite_2.0/UnsafeNativeMethods.cs"

Second, when i call conn.ChangePassword("testpassword") it throws an exception: System.EntryPointNotFoundException: Unable to find an entry point named "sqlite3_rekey" in DLL "sqlite3"

#if !PLATFORM_COMPACTFRAMEWORK
    [DllImport(SQLITE_DLL, CallingConvention = CallingConvention.Cdecl)]
#else
    [DllImport(SQLITE_DLL)]
#endif
    internal static extern int sqlite3_key(IntPtr db, byte[] key, int keylen);

Third, using URI=file:{0};Password=testpassword with the already encrypted database throws an exception: System.EntryPointNotFoundException: Unable to find an entry point named "sqlite3_key" in DLL "sqlite3"

#if !PLATFORM_COMPACTFRAMEWORK
    [DllImport(SQLITE_DLL, CallingConvention = CallingConvention.Cdecl)]
#else
    [DllImport(SQLITE_DLL)]
#endif
    internal static extern int sqlite3_rekey(IntPtr db, byte[] key, int keylen);

The matching sqlite.h defines:

...
SQLITE_API int SQLITE_STDCALL sqlite3_rekey
...
SQLITE_API int SQLITE_STDCALL sqlite3_key
...

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