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.NET获取Access新增记录Id怪现象

编辑:dnawo 日期:2012-03-01

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写了一个函数获取Access表中指定用户Id，要求当传入的用户名不存在时，则在表中新增一条记录并返回Id。

复制内容到剪贴板程序代码 程序代码
using System;
using System.Data.OleDb;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(GetUserId("dnawo"));
            Console.ReadKey();
        }

        /// <summary>
        /// 获取用户Id
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        static int GetUserId(string name)
        {
            using (OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=F:\db1.mdb"))
            {
                conn.Open();
                using (OleDbCommand cmd = new OleDbCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText = "select Id from UserTB where UserName='" + name + "'";
                    object val = cmd.ExecuteScalar();

                    if (val != null)
                        return int.Parse(val.ToString());
                    else
                    {
                        cmd.CommandText = string.Format("insert into UserTB(UserName) values('{0}')", name);
                        cmd.ExecuteNonQuery();

                        return GetUserId(name);
                    }
                }
                conn.Close();
            }
        }
    }
}

经测试，当用户不存在时，执行上边代码后Access表中总会新增两条一样的记录：



改用SQL Server数据库不会有上述问题，经多次测试又发现，若在"return GetUserId(name);"处设置断点，稍停一会也不会出现上述问题。最终代码修改如下运行正常：

复制内容到剪贴板程序代码 程序代码
using System;
using System.Data.OleDb;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(GetUserId("dnawo"));
            Console.ReadKey();
        }

        /// <summary>
        /// 获取用户Id
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        static int GetUserId(string name)
        {
            int id = 0;

            using (OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=F:\db1.mdb"))
            {
                conn.Open();
                using (OleDbCommand cmd = new OleDbCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText = "select Id from UserTB where UserName='" + name + "'";
                    object val = cmd.ExecuteScalar();

                    if (val != null)
                        id = int.Parse(val.ToString());
                    else
                    {
                        cmd.CommandText = string.Format("insert into UserTB(UserName) values('{0}')", name);
                        cmd.ExecuteNonQuery();
                    }
                }
                conn.Close();
            }

            return id == 0 ? GetUserId(name) : id;
        }
    }
}


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