`System.Linq.Dynamic` library will help you generating dynamic query which has extension method

Where(string predicate,params object[] values)

包含命名空间

using System.Linq.Dynamic;

然后在运行时构造谓词

string predicate = "OrderId = @0";
int identity_value = 5;

然后查询db.Orders

then query db.Orders

db.Orders.AsQueryable().Where(predicate,identity_value);