我有一个Person对象列表。我想转换为Dictionary，其中键是第一个和最后一个名字(连接)，值是Person对象。
问题是我有一些重复的人，所以这爆炸如果我使用以下代码:
private Dictionary<string, Person> _people = new Dictionary<string, Person>();
_people = personList.ToDictionary(
e => e.FirstandLastName,
StringComparer.OrdinalIgnoreCase);
我知道这听起来很奇怪，但我现在真的不关心重复的名字。如果有多个名字，我只想取一个。有没有什么方法可以让上面的代码只取其中一个名字而不会重复?
当前回答
要处理消除重复，实现一个IEqualityComparer<Person>，可以在Distinct()方法中使用，然后获取字典就很容易了。 考虑到:
class PersonComparer : IEqualityComparer<Person>
{
public bool Equals(Person x, Person y)
{
return x.FirstAndLastName.Equals(y.FirstAndLastName, StringComparison.OrdinalIgnoreCase);
}
public int GetHashCode(Person obj)
{
return obj.FirstAndLastName.ToUpper().GetHashCode();
}
}
class Person
{
public string FirstAndLastName { get; set; }
}
拿出你的字典:
List<Person> people = new List<Person>()
{
new Person() { FirstAndLastName = "Bob Sanders" },
new Person() { FirstAndLastName = "Bob Sanders" },
new Person() { FirstAndLastName = "Jane Thomas" }
};
Dictionary<string, Person> dictionary =
people.Distinct(new PersonComparer()).ToDictionary(p => p.FirstAndLastName, p => p);
其他回答
您还可以使用ToLookup LINQ函数，然后您几乎可以与Dictionary互换使用该函数。
_people = personList
.ToLookup(e => e.FirstandLastName, StringComparer.OrdinalIgnoreCase);
_people.ToDictionary(kl => kl.Key, kl => kl.First()); // Potentially unnecessary
这将在LukeH的回答中执行GroupBy，但将给出Dictionary提供的散列。因此，您可能不需要将它转换为Dictionary，但只要在需要访问键的值时使用LINQ First函数即可。
LINQ的解决方案:
// Use the first value in group
var _people = personList
.GroupBy(p => p.FirstandLastName, StringComparer.OrdinalIgnoreCase)
.ToDictionary(g => g.Key, g => g.First(), StringComparer.OrdinalIgnoreCase);
// Use the last value in group
var _people = personList
.GroupBy(p => p.FirstandLastName, StringComparer.OrdinalIgnoreCase)
.ToDictionary(g => g.Key, g => g.Last(), StringComparer.OrdinalIgnoreCase);
如果你更喜欢非linq解决方案，那么你可以这样做:
// Use the first value in list
var _people = new Dictionary<string, Person>(StringComparer.OrdinalIgnoreCase);
foreach (var p in personList)
{
if (!_people.ContainsKey(p.FirstandLastName))
_people[p.FirstandLastName] = p;
}
// Use the last value in list
var _people = new Dictionary<string, Person>(StringComparer.OrdinalIgnoreCase);
foreach (var p in personList)
{
_people[p.FirstandLastName] = p;
}
从Carra的解开始，你也可以把它写成:
foreach(var person in personList.Where(el => !myDictionary.ContainsKey(el.FirstAndLastName)))
{
myDictionary.Add(person.FirstAndLastName, person);
}
下面是一个明显的非linq解决方案:
foreach(var person in personList)
{
if(!myDictionary.ContainsKey(person.FirstAndLastName))
myDictionary.Add(person.FirstAndLastName, person);
}
如果你不介意总是添加最后一个，你可以避免这样的双重查找:
foreach(var person in personList)
{
myDictionary[person.FirstAndLastName] = person;
}
要处理消除重复，实现一个IEqualityComparer<Person>，可以在Distinct()方法中使用，然后获取字典就很容易了。 考虑到:
class PersonComparer : IEqualityComparer<Person>
{
public bool Equals(Person x, Person y)
{
return x.FirstAndLastName.Equals(y.FirstAndLastName, StringComparison.OrdinalIgnoreCase);
}
public int GetHashCode(Person obj)
{
return obj.FirstAndLastName.ToUpper().GetHashCode();
}
}
class Person
{
public string FirstAndLastName { get; set; }
}
拿出你的字典:
List<Person> people = new List<Person>()
{
new Person() { FirstAndLastName = "Bob Sanders" },
new Person() { FirstAndLastName = "Bob Sanders" },
new Person() { FirstAndLastName = "Jane Thomas" }
};
Dictionary<string, Person> dictionary =
people.Distinct(new PersonComparer()).ToDictionary(p => p.FirstAndLastName, p => p);
