Question

我已完成动态linq表达式，如下所示

private static List<Employee> FilterData(
    IQueryable<system> systemData, 
    IQueryable<employee> employeeData)
{
    var filterData = systemData.Join(
        employeeData,
        s => s.id, em => em.system_id, 
        (systemEntity, employeeEntity) => new { employee = employeeEntity});
}

在Join中使用Generic时如何进行以下连接？如何实现s =＆gt; s.id，em =＆gt; em.system_id

private static List<TEntity> FilterData(
    IQueryable<T> systemData, 
    IQueryable<TEntity> employeeData)
{
    //var filterData = systemData.Join(
    //    employeeData,
    //    s => s.id, em => em.system_id, 
    //    (systemEntity, employeeEntity) => new { employee = employeeEntity});
}

Answer 1

您可以为方法添加通用约束：

public interface ISystem
{
  int id { get; }
  ...
}

public interface IEmployee
{
  ...
  int system_id { get; }
  ...
}

private static List<TEmployee> FilterData<TSystem, TEmployee>(
  IQueryable<TSystem> systemData, IQueryable<TEmployee> employeeData)
  where TSystem : ISystem
  where TEmployee: IEmployee
{
  var filterData = 
      systemData.Join(employeeData,
                      s => s.id, 
                      em => em.system_id, 
                      (systemEntity, employeeEntity) => new { employee = employeeEntity});
}

请注意，您似乎只对使用现有system_id的员工感兴趣，如果是这种情况，加入可能是过度的（如果您从系统中提取属性则不会）

如何设置Join for IQueryable <t> linq表达式

1 个答案: