求LinQ 更新字段语法
SQL

SQL code

update Table set col1 = '123' where id = 3

怎样把他转换为LinQ语法，在一个List<Entity>集合里面.不是LinQ to Sql的，我只是想把一个对象里面某个字段的值做一下修改。

[解决办法]
(from e in List<Entity>
where e.id==3
select e).FirstOrDefault().coll="123";
[解决办法]
List<Entity>.ForEach(e=> {if(e.id==3)e.col1="123";});
[解决办法]
写一个扩展,大概思路是这样的，发我在实际中的转化

C# code

  static class UpdateExtensions    {        private static Command GetCommands<Entity>(Expression<Func<Entity, bool>> Predicate, Expression<Func<Entity, Entity>> Updater) where Entity : class,IEntity        {            ConditionBuilder Builder = new ConditionBuilder();            Builder.Build(Predicate.Body);            string sqlCondition = Builder.Condition;            //获取Update的赋值语句            var updateMemberExpr = (MemberInitExpression)Updater.Body;            var updateMemberCollection = updateMemberExpr.Bindings.Cast<MemberAssignment>().Select(c => new            {                Name = c.Member.Name,                Value = ((ConstantExpression)c.Expression).Value            });            int i = Builder.Arguments.Length;            Type type = typeof(Entity);            var tableAttribute = type.GetCustomAttributes(false).OfType<System.ComponentModel.DataAnnotations.TableAttribute>().FirstOrDefault();            string Table = tableAttribute == null ? type.Name : tableAttribute.Name;            if (Table.Length > 2 && Table.StartsWith("DB", StringComparison.CurrentCultureIgnoreCase))            {                Table = Table.Substring(2, Table.Length - 2);            }            var PreTable = System.Configuration.ConfigurationManager.AppSettings["PreTable"];            Table = PreTable == null ? Table : PreTable + "_" + Table;            string sqlUpdateBlock = string.Join(", ", updateMemberCollection.Select(c => string.Format("[{0}]={1}", c.Name, "{" + (i++) + "}")).ToArray());            string commandText = string.Format("Update [{0}] Set {1} Where {2}", Table, sqlUpdateBlock, sqlCondition);            //获取SQL参数数组 (包括查询参数和赋值参数)            var args = Builder.Arguments.Union(updateMemberCollection.Select(c => c.Value)).ToArray();            return new Command() { Text = commandText, args = args };        }        /// <summary>        /// 执行UpDate返回影响的条数        /// </summary>        public static int UpdateEntity<Entity>(this EFDbContext<Entity> Context, Expression<Func<Entity, bool>> Predicate, Expression<Func<Entity, Entity>> Updater) where Entity : class,IEntity        {            Command com = GetCommands<Entity>(Predicate, Updater);            int Result = Context.Database.ExecuteSqlCommand(com.Text, com.args);            return Result;        }