Expression多条件筛选

使用场景：多条件筛选，不确定条件的个数时，可选择此种方式；

扩展类：

public static class ExpLinqExpressions
   {
       public static Expression<Func<T, bool>> True<T>()
       {
           return f => true;
       }
       public static Expression<Func<T, bool>> False<T>()
       {
           return f => false;
       }
       public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
       { 
           var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); 
           return Expression.Lambda<Func<T, bool>>(Expression.Or(expr1.Body, invokedExpr), expr1.Parameters); 
       }
       public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) 
       {
           var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); 
           return Expression.Lambda<Func<T, bool>>(Expression.And(expr1.Body, invokedExpr), expr1.Parameters); 
       }
   }

使用样例：

#region 多条件筛选
         ///查询数据库的仓储类
         ItestRepository test = new TestRepository();
         test.FindAll(d => d.Id == 1);
         Expression<Func<Test, bool>> pre;
         pre = s => s.Id == 1;
         int money = 10;
         if (money > 0)
         {
             pre = pre.And(d => d.Money == money);
         }
 
         var vlus = test.FindAll(pre.Compile());
         #endregion