LINQ动态条件查询问题？
这两天在研究LINQ动态查询，但是自己把网上拿来东西在根据自己需要在变通一下就有问题了，请帮忙解决下，我已在本机上调试很多次都有问题的~

C# code

IQueryable<Customer> custs = db.Customers;  改成IQueryable<Customer> custs = db.Customers.Where(c=>c.City=="London");//先筛选再动态查询ParameterExpression param =     Expression.Parameter(typeof(Customer), "c");Expression selector = Expression.Property(param,    typeof(Customer).GetProperty("ContactName"));Expression pred = Expression.Lambda(selector, param);Expression expr = Expression.Call(typeof(Queryable), "Select",    new Type[] { typeof(Customer), typeof(string) },    Expression.Constant(custs), pred);IQueryable<string> query = db.Customers.AsQueryable()    .Provider.CreateQuery<string>(expr);   //经过上面的筛选调试结果为空？请问能否这样？System.Data.Common.DbCommand cmd = db.GetCommand(query);Console.WriteLine(cmd.CommandText);IQueryable<Customer> custs = db.Customers;ParameterExpression param =   Expression.Parameter(typeof(Customer), "c");Expression left = Expression.Property(param,    typeof(Customer).GetProperty("City"));Expression right = Expression.Constant("London");Expression filter = Expression.Equal(left, right);Expression pred = Expression.Lambda(filter, param);MethodCallExpression whereCallExpression = Expression.Call(    typeof(Queryable), "Where",    new Type[] { typeof(Customer) },    Expression.Constant(custs), pred);//OrderBy(ContactName => ContactName)MethodCallExpression orderByCallExpression = Expression.Call(    typeof(Queryable), "OrderBy",    new Type[] { typeof(Customer), typeof(string) },     whereCallExpression,    Expression.Lambda(Expression.Property    (param, "ContactName"), param));//生成动态查询IQueryable<Customer> query = db.Customers.AsQueryable()    .Provider.CreateQuery<Customer>(orderByCallExpression);

上面代码实现了where orderby动态查询，请问怎么同时实现SELECT where 或 SELECT where orderby查询，我试了很多次修改，都不行？现在感觉LINQ动态查询很难满足平时项目中的需要，请问有什么好的办法吗？

[解决办法]
你写一个sql，一下自己就明白了。

你写这一大堆莫名其妙的“Linq”代码，我真的很同情Linq啊。这是把Linq抬高了之后重重地扔在阴沟里捧杀。呵呵呵呵。