使用LINQ和C#查询Microsoft Access MDB数据库

Question

我有一个*.MDB数据库文件,我想知道是否有可能或建议在C#中使用LINQ来对付它.我也想知道一些简单的例子会是什么样子.

我对LINQ知之甚少,但我对此任务的要求非常简单(我相信).用户将传递给Microsoft Access MDB数据库的文件路径,我想使用LINQ将行添加到数据库中的一个表.

Answer 1

你想要的是LINQ to ODBC提供程序,或LINQ to JET/OLEDB提供程序.

开箱即用,MS没有制作一个.可能有第三方.

Answer 2

实际上我最近(今天)发现你可以使用LinqToSql访问Access数据库.它必须是2002或更新的格式,您将无法将表拖放到datacontext中,因此可以在dbml中手动创建对象,也可以使用SQL Server Migration for Access将其移动到sql server和然后拖放你想要的一切.当您想要实际创建上下文时,将其传递给OleDbConnection.在OleDbConnection上使用标准的Jet.OLEDB.4.0连接字符串,你很高兴.不确定这可能会产生的限制.我刚做了一个快速的样本并且没有问题就做了OrderBy.

Answer 3

我写了一个小样本程序来测试David的回答.您需要创建一个访问数据库并手动创建Linq-to-SQL的DBML,因为您无法拖放它们.

插入失败,引用Missing semicolon (;) at end of SQL statement.但查询似乎正常.

using System;
using System.Collections.Generic;
using System.Data.OleDb;
using System.IO;
using System.Linq;
using Linq2Access.Data;

namespace Linq2Access
{
    class Program
    {
        static readonly string AppPath = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
        static readonly string DbPath = Path.Combine(AppPath, "Data", "database.accdb");
        static readonly string DbConnString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + DbPath + "';Persist Security Info=False;";

        static void Main(string[] args)
        {
            if (!File.Exists(DbPath))
                throw new Exception("Database file does not exist!");

            using (OleDbConnection connection = new OleDbConnection(DbConnString))
            using (DataRepositoryDataContext db = new DataRepositoryDataContext(connection))
            {
                List<dbProject> projects = new List<dbProject>();
                for (int i = 1; i <= 10; i++)
                {
                    dbProject p = new dbProject() { Title = "Project #" + i };
                    for (int j = 1; j <= 10; j++)
                    {
                        dbTask t = new dbTask() { Title = "Task #" + (i * j) };
                        p.dbTasks.Add(t);
                    }
                    projects.Add(p);
                }

                try
                {
                    //This will fail to submit
                    db.dbProjects.InsertAllOnSubmit(projects);
                    db.SubmitChanges();
                    Console.WriteLine("Write succeeded! {0} projects, {1} tasks inserted",
                                        projects.Count,
                                        projects.Sum(x => x.dbTasks.Count));
                }
                catch(Exception ex)
                {
                    Console.WriteLine("Write FAILED. Details:");
                    Console.WriteLine(ex);
                    Console.WriteLine();
                }

                try
                {
                    //However, if you create the items manually in Access they seem to query fine
                    var projectsFromDb = db.dbProjects.Where(x => x.Title.Contains("#1"))
                                                        .OrderBy(x => x.ProjectID)
                                                        .ToList();

                    Console.WriteLine("Query succeeded! {0} Projects, {1} Tasks",
                                        projectsFromDb.Count,
                                        projectsFromDb.Sum(x => x.dbTasks.Count));
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Query FAILED. Details:");
                    Console.WriteLine(ex);
                    Console.WriteLine();
                }

                Console.WriteLine();
                Console.WriteLine("Press any key to continue...");
                Console.ReadKey();
            }
        }
    }
}