OS X上的Mono:System.Data.SQLite不起作用

Question

我打算用Mono和SQLite作为数据库来做一个项目.开发主要在Mac上完成.我已成功设置Mono并测试了System.Data.SQLite(托管dll).简单的测试应用程序完美运

但是,当我尝试DataTable在我的代码中使用时,它会抛出运行时异常.以下是代码段:

public static void Main (string[] args)
{
    string connectionString = "Data Source=emp.db";

    try {
        using (SQLiteConnection conn = new SQLiteConnection(connectionString))
        {
            string query = "SELECT firstname, lastname FROM employees";

            using (SQLiteCommand comm = new SQLiteCommand(query, conn))
            {
                conn.Open();

                comm.CommandText = query;

                using (SQLiteDataReader reader = comm.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        string firstname = reader.GetString(0);
                        string lastname  = reader.GetString(1);
                        Console.WriteLine("Name: " + firstname + " " + lastname);
                    }

                    DataTable dt = new DataTable();
                    dt.Load(reader);  // line 39 where problem occurs
                }
            }
        }
    } catch (Exception e) {
        Console.WriteLine(e);
    }
}

上面的代码成功构建,但不在我的开发机器上运行,并在终端上提供以下输出.

运行应用程序时的输出如下:

Name: John Doe
Name: Eric Smith
System.EntryPointNotFoundException: sqlite3_column_origin_name
  at (wrapper managed-to-native) System.Data.SQLite.UnsafeNativeMethods:sqlite3_column_origin_name (intptr,int)
  at System.Data.SQLite.SQLite3.ColumnOriginalName (System.Data.SQLite.SQLiteStatement stmt, Int32 index) [0x00000] in <filename unknown>:0 
  at System.Data.SQLite.SQLiteDataReader.GetSchemaTable (Boolean wantUniqueInfo, Boolean wantDefaultValue) [0x00000] in <filename unknown>:0 
  at System.Data.SQLite.SQLiteDataReader.GetSchemaTable () [0x00000] in <filename unknown>:0 
  at System.Data.Common.DataAdapter.BuildSchema (IDataReader reader, System.Data.DataTable table, SchemaType schemaType, MissingSchemaAction missingSchAction, MissingMappingAction missingMapAction, System.Data.Common.DataTableMappingCollection dtMapping) [0x0003b] in /private/tmp/monobuild/build/BUILD/mono-2.10.6/mcs/class/System.Data/System.Data.Common/DataAdapter.cs:284 
  at System.Data.DataTable.Load (IDataReader reader, LoadOption loadOption) [0x0001f] in /private/tmp/monobuild/build/BUILD/mono-2.10.6/mcs/class/System.Data/System.Data/DataTable.cs:2853 
  at System.Data.DataTable.Load (IDataReader reader) [0x00011] in /private/tmp/monobuild/build/BUILD/mono-2.10.6/mcs/class/System.Data/System.Data/DataTable.cs:2838 
  at SQLiteApp.MainClass.Main (System.String[] args) [0x00086] in /Users/nayaabkhan/Projects/SQLiteApp/SQLiteApp/Main.cs:37

我很惊讶地看到上面相同的可执行文件在Windows下完美运行,但在我的开发机器上失败了.

在互联网上搜索,我发现这个问题必须与sqlite动态库有关,必须用SQLITE_ENABLE_COLUMN_METADATA编译.我也尝试用SQLITE_ENABLE_COLUMN_METADATA编译sqlite.我不知道在哪里编译libsqlite3.0.dylib.

任何帮助将不胜感激.

Answer 1

你需要将dylib放在mono可以找到它的任何地方.

您可以通过执行以下操作找到mono查找本机库的位置:

export MONO_LOG_LEVEL=debug
export MONO_LOG_MASK=dll
mono yourprogram.exe

并且详细的查找输出将打印到终端.在我的系统上,mono首先在可执行文件所在的目录中查找,因此将dylib放在那里可能是最简单的.然后mono要求系统找到dylib(通过尝试在没有路径的情况下打开它).系统通常查找/ usr/lib以及其他一些地方(这当然是系统相关的),但无论如何,您可以通过将LD_LIBRARY_PATH设置为该路径来为系统添加路径.在这种情况下,你会这样做:

export LD_LIBRARY_PATH=/path/to/dylib:$LD_LIBRARY_PATH
mono yourprogram.exe