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[英]get values from nested Dictionary using LINQ. Values of Dictionary are list of lists
[英]LINQ. Update one dictionary from corresponding values in another joined by key
我必须去字典
dic1<double, double>
dic2<double, double>
长度可能不匹配。 因此,我需要从由dic1.key == dic2.key加入的dic2中更新dic1中的值。但是要保留dic1中没有相应键的那些值。
.NET是3.5
您可以仅遍历dic2中的值:
Dictionary<double, double> dic1;
Dictionary<double, double> dic2;
foreach (var pair in dic2)
{
dic1[pair.Key] = pair.Value;
}
或者,如果要更新但不插入,请检查密钥是否存在:
foreach (var pair in dic2)
{
if (dic1.ContainsKey(pair.Key))
{
dic1[pair.Key] = pair.Value;
}
}
编辑:如果您确实要使用Linq,则可能要创建一个新字典,而不是更新现有字典:
dic1 =
(from pair in dic1
let Value = dic2.ContainsKey(pair.Key) ? dic2[pair.Key] : pair.Value
select new { pair.Key, Value }
).ToDictionary(pair => pair.Key, pair => pair.Value);
要么
dic1 =
(from pair in dic1
join pair2 in dic2 on pair.Key equals pair2.Key into g
select new { pair.Key, g.DefaultIfEmpty(pair).First().Value }
).ToDictionary(pair => pair.Key, pair => pair.Value);
我认为,这只会增加阅读难度。
这是Linq外部左联接版本:
Dictionary<double, double> dictionary =
(from d1 in dic1
join d2 in dic2 on d1.Key equals d2.Key into kvp
from nv in kvp.DefaultIfEmpty(d1)
select nv).ToDictionary(x => x.Key, x => x.Value);
尝试这个:
var entries = dic2.Where(x => dic1.ContainsKey(x.Key));
foreach (KeyValuePair<double, double> entry in entries)
{
dic1[entry.Key] = entry.Value;
}
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