linq to sql 给我们带来很多惊奇的地方，减少我们的代码，节省了我们的时间，但是为了更方便做了一些小的扩展，部分内容来自网络。

      通过实体类插叙db.find<T>(T t):

  public IQueryable<TEntity> Find<TEntity>(TEntity obj) where TEntity : class
        {
            //获得所有property的信息
            PropertyInfo[] properties = obj.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);
            //构造初始的query
        
            IQueryable<TEntity> query = this.GetTable<TEntity>().AsQueryable<TEntity>();
            //遍历每个property
            foreach (PropertyInfo p in properties)
            {
                if (p != null)
                {
                    Type t = p.PropertyType;
                    //加入object，Binary，和XDocument， 支持sql_variant，imager 和xml等的影射。
                    if (t.IsValueType || t == typeof(string) || t == typeof(System.Byte[])
                      || t == typeof(object) || t == typeof(System.Xml.Linq.XDocument)
                      || t == typeof(System.Data.Linq.Binary))
                    {
                        //如果不为null才算做条件

                        if (p.GetValue(obj, null) != null)
                        {
                            if (((ColumnAttribute)(p.GetCustomAttributes(typeof(ColumnAttribute), true)[0])).IsPrimaryKey && Convert.ToInt32(p.GetValue(obj, null)) == 0)
                            {

                            }
                            else
                            {

                              //构造linq 表达式
                                ParameterExpression param = Expression.Parameter(typeof(TEntity),"c");
                                Expression right = Expression.Constant(p.GetValue(obj, null));
                                Expression left = Expression.Property(param, p.Name);
                                Expression filter = Expression.Equal(left, right);
                                Expression<Func<TEntity, bool>> pred = Expression.Lambda<Func<TEntity, bool>>(filter, param);
                                query = query.Where(pred);
                            }
                        }
                    }
                }
            }
            return query;
        }

      通过类的主键查询：

 public TEntity FindKey<TEntity>(object value) where TEntity : class
        {
            //获得所有property的信息
            PropertyInfo[] properties = typeof(TEntity).GetProperties(BindingFlags.Public | BindingFlags.Instance);
            //构造初始的query
            IQueryable<TEntity> query = this.GetTable<TEntity>().AsQueryable<TEntity>();
            //遍历每个property
            foreach (PropertyInfo p in properties)
            {
                if (p != null)
                {
                    Type t = p.PropertyType;
                    //加入object，Binary，和XDocument， 支持sql_variant，imager 和xml等的影射。
                    if (t.IsValueType || t == typeof(string) || t == typeof(System.Byte[])
                      || t == typeof(object) || t == typeof(System.Xml.Linq.XDocument)
                      || t == typeof(System.Data.Linq.Binary))
                    {
                        //如果不为null才算做条件

                        if (((ColumnAttribute)(p.GetCustomAttributes(typeof(ColumnAttribute), true)[0])).IsPrimaryKey)
                        {
                            ParameterExpression param = Expression.Parameter(typeof(TEntity), "d");
                            Expression right = Expression.Constant(value);
                            Expression left = Expression.Property(param, p.Name);
                            Expression filter = Expression.Equal(left, right);

                            Expression<Func<TEntity, bool>> pred = Expression.Lambda<Func<TEntity, bool>>(filter, param);

                            query = query.Where(pred);
                            break;

                        }

                    }
                }
            }
            return query.First();
        }

    }

      通过实体类更新：

public void Update<TEntity>(TEntity obj) where TEntity : class
        {
            string str = "update  [" + typeof(TEntity).Name + "] set ";
            string cols = "";
            string where="";
            //获得所有property的信息
            PropertyInfo[] properties = obj.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);
            //构造初始的query

            IQueryable<TEntity> query = this.GetTable<TEntity>().AsQueryable<TEntity>();
            //遍历每个property
            foreach (PropertyInfo p in properties)
            {
                if (p != null)
                {
                    Type t = p.PropertyType;
                    //加入object，Binary，和XDocument， 支持sql_variant，imager 和xml等的影射。
                    if (t.IsValueType || t == typeof(string) || t == typeof(System.Byte[])
                      || t == typeof(object) || t == typeof(System.Xml.Linq.XDocument)
                      || t == typeof(System.Data.Linq.Binary))
                    {
                        //如果不为null才算做条件

                        if (p.GetValue(obj, null) != null)
                        {
                            if (((ColumnAttribute)(p.GetCustomAttributes(typeof(ColumnAttribute), true)[0])).IsPrimaryKey)
                            {
                                where +=" where ["+p.Name+"]="+p.GetValue(obj,null);
                            }
                            else
                            {

                                if (!(t.ToString().ToLower().Contains("string") || t.ToString().ToLower().Contains("datetime")))
                                    cols += "["+p.Name + "]=" + p.GetValue(obj, null) + ",";
                                else
                                    cols += "["+p.Name + "]='" + p.GetValue(obj, null) + "',";
                            }
                        }
                    }
                }
            }

            str += cols.Substring(0,cols.Length-1) +where;
             HttpContext.Current.Response.Write("<br>"+str+"<br>");
             this.ExecuteCommand(str);
         
        }
        public void UpdateAll<TEntity>(IEnumerable<TEntity> obj) where TEntity : class
        {
            foreach (var item in obj)
            {
                this.Update<TEntity>(item);
            }
        }

  更新、删除、添加代码类似，也可以实现多条数据的数据操作。代码和更新类似。代码下载地址http://fccms.googlecode.com/files/linqtoaccess.rar 里面得db.cs文件里。