Linqu动态查询

Posted 2020-11-03

public class ExpressionCall
    {
        List<Customer> customers = new List<Customer>() {
            new Customer() { CustomerID = "A001"},
            new Customer() { CustomerID = "A"},
            new Customer() { CustomerID = "B001" },
    };
        string[] starts = { "A", "C", "D" };
        public void SelectMore()
        {  //根据CustomerID首字母 包含A,C,D动态创建查询
            IQueryable<Customer> cus = customers.AsQueryable();
            ParameterExpression c = Expression.Parameter(typeof(Customer), "c");
            Expression condition = Expression.Constant(false);
            foreach (string s in starts)
            {
                Expression con = Expression.Call(
                    Expression.Property(c, typeof(Customer).GetProperty("CustomerID")),
                    typeof(string).GetMethod("Equals", new Type[] { typeof(string) }),
                    Expression.Constant(s));
                condition = Expression.Or(con, condition);
            }
            Expression<Func<Customer, bool>> end =
                Expression.Lambda<Func<Customer, bool>>(condition, new ParameterExpression[] { c });
            var cu = cus.Where(end);
        }
    }
    public class Customer
    {
        public string CustomerID { get; set; }
    }

View Code

代码如上，参考：http://www.cnblogs.com/blusehuang/archive/2007/07/13/816970.html

其中包含。首字母包含

                    typeof(string).GetMethod("StartsWith", new Type[] { typeof(string) }),

                    typeof(string).GetMethod("Contains", new Type[] { typeof(string) }),