我们知道LINQ中的增删改都要调用SubmitChanges方法，我们记录所有SQL的方式就是重写（override）DataContext中的SubmitChanges方法，为了避免每次修改dbml文件时影响我们自己写的内容，我们要先写一个DataContext的分布类，在这个类中重写SubmitChanges方法。
代码如下
Code
public partial class DataClasses1DataContext
    {
        public override void SubmitChanges(System.Data.Linq.ConflictMode failureMode)
        {
            //记录日志（每天一个文件，记录所有更改sql,日志会存在第一个盘的log文件夹下）
            string directory = Path.Combine(Directory.GetLogicalDrives().First(), "log");
            Directory.CreateDirectory(directory);
            string logFile = Path.Combine(directory,
                "log" + DateTime.Now.ToLongDateString() + ".txt");
            using (StreamWriter w = File.AppendText(logFile))
            {
              
                w.WriteLine("发生时间:{0}", DateTime.Now.ToString());
                w.WriteLine("日志内容为:");
                this.Log = w;
                try
                {
                    base.SubmitChanges(failureMode);
                }
                catch (Exception e)
                {
                    w.WriteLine("异常：" + e.Message + e.StackTrace);
                    w.WriteLine("--------------------------------------------------------------");

                    throw;
                }
                finally
                {
                    this.Log = null;
                }
                w.WriteLine("--------------------------------------------------------------");

            }

        }
    }
 

如果想把sql语句全部记录到数据库的代码如下：

Code
public partial class DataClasses1DataContext
    {
        StringBuilder sb = new StringBuilder();
            using (StringWriter sw = new StringWriter(sb))
            {

                sw.WriteLine("发生时间:{0}", DateTime.Now.ToString());
                sw.WriteLine("日志内容为:");
                this.Log = sw;
                try
                {
                    base.SubmitChanges(failureMode);
                    string sqlStr = "insert into logTable(Content)values( '"+sb.ToString()+"')";
                    //SqlConnection con=
                    using (SqlConnection con=new SqlConnection(this.Connection.ConnectionString))
                    {
                        con.Open();
                        SqlCommand cmd = new SqlCommand(sqlStr, con);
                        cmd.ExecuteNonQuery();
                    }

                }
                catch (Exception e)
                {
                    //记录日志（每天一个文件，记录所有更改sql,日志会存在第一个盘的log文件夹下）

                    string directory = Path.Combine(Directory.GetLogicalDrives().First(), "log");
                    Directory.CreateDirectory(directory);
                    string logFile = Path.Combine(directory,
                        "log" + DateTime.Now.ToLongDateString() + ".txt");
                    using (StreamWriter w = File.AppendText(logFile))
                    {
                        w.WriteLine("发生时间:{0}", DateTime.Now.ToString());
                        w.WriteLine("日志内容为:");
                        w.WriteLine(e.Message);

                    }
                }
                finally
                {
                    this.Log = null;
                }
    }
 

源码下载
http://files.cnblogs.com/nuaalfm/LogLinqSql.rar
http://www.cnblogs.com/nuaalfm/archive/2009/01/20/1378841.html