linq 基于var动态查询
有三表，表名A,B,C
字段
A : id name sex phone
B : id Aid Bid
C : id dept keyword


前提
var joinTable = from a in A
  join b in B on b.Aid equals a.id
  join c in C on b.Cid equals C.id
  select new
  {
  aid = a.id,aname = a.name,cdept = c.dept,ckeyword = c.keyword
  }

遇到的问题：
对joinTable 做动态查询怎么写 比如：对名字、性别、电话、部门、关键字 做动态查询
如：构建 
ParameterExpression pe = Expression.Parameter(typeof(User), "s");
Expression left;

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Dynamic LINQ
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http://blog.csdn.net/sandy945/article/details/5735326