c# - 减少类似查询的重复

Question

Possible Duplicate:
How can I send where statements to a method which are dynamically executed in a LINQ statement?

我一直在单独的方法中编写简单的 LINQ 查询，但它们变得重复。请原谅名称和地点的愚蠢示例，所有三种方法中唯一发生变化的部分是“where”子句。

如何让这段重复的代码变得更多dry ？

例如，类似于辅助方法的东西，它采用相同的所有内容，但允许在 where 子句中进行更改。

public IEnumerable<NamePlace> GetSomeData(int num1, int num2)
{
  var temp = from Name in Names
             from Place in Places
             where Name.id == num1 && Place.id = num2
             select new NamePlace {
                  field1 = Name.name;
                  field2 = Place.name;
             };
  return temp;
}

public IEnumerable<NamePlace> GetSomeData2(int num1, int num2)
{
  var temp = from Name in Names
             from Place in Places
             where Name.age == num1 && Place.streetNumber = num2
             select new NamePlace {
                  field1 = Name.name;
                  field2 = Place.name;
             };
  return temp;
}

public IEnumerable<NamePlace> GetSomeData3(int num1, int num2)
{
  var temp = from Name in Names
             from Place in Places
             where Name.favouriteNumber == num1 && Place.neighbourNumber = num2
             select new NamePlace {
                  field1 = Name.name;
                  field2 = Place.name;
             };
  return temp;
}

Answer 1

您所需要的只是 Func<T1, T2, bool> 类型的参数哪里T1和T2是 Names 中项目的类型和Places分别。

private IEnumerable<NamePlace> GetSomeDataHelper(Func<Name, Place, bool> filter)
{
  var query = from name in Names
             from place in Places
             where filter(name, place)
             select new NamePlace {
                  field1 = name.name,
                  field2 = place.name,
             };
  return query;
}

public IEnumerable<NamePlace> GetSomeData1(int num1, int num2)
{
    return GetSomeDataHelper((name, place) => name.id == num1 && place.id = num2);
}