if(mymember.isuser(uid))
{
DBnameEntities db;
db = new DBnameEntities();
var objA = db.A.Where(t => t.uid == uid).FirstOrDefault();
...
db.SaveChanges();

db = new DBnameEntities();
var objB = db.B.Where(t => t.uid == uid).FirstOrDefault();
...
db.SaveChanges();

db = new DBnameEntities();
var objC = db.C.Where(t => t.uid == uid).FirstOrDefault();
...
db.SaveChanges();

db = new DBnameEntities();
var objD = db.D.Where(t => t.uid == uid).FirstOrDefault();
...
db.SaveChanges();
}
.........
数据插入也差不多做法，这里省