C# 根据值删除字典中的项目
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Remove Item in Dictionary based on Value
提问by Jon
I have a Dictionary<string, string>.
我有一个Dictionary<string, string>.
I need to look within that dictionary to see if a value exists based on input from somewhere else and if it exists remove it.
我需要在该字典中查看是否存在基于其他地方输入的值，如果存在则将其删除。
ContainsValue just says true/false and not the index or key of that item.
containsValue 只是说真/假，而不是该项目的索引或键。
Help!
帮助！
Thanks
谢谢
EDIT:Just found this - what do you think?
编辑：刚刚发现这个 - 你怎么看？
var key = (from k in dic where string.Compare(k.Value, "two", true) ==
0 select k.Key).FirstOrDefault();
EDIT 2:I also just knocked this up which might work
编辑 2：我也刚刚敲了这可能有用
foreach (KeyValuePair<string, string> kvp in myDic)
{
if (myList.Any(x => x.Id == kvp.Value))
myDic.Remove(kvp.Key);
}
采纳答案by Paul Turner
Are you trying to remove a single value or all matching values?
您是要删除单个值还是所有匹配的值？
If you are trying to remove a single value, how do you define the value you wish to remove?
如果您尝试删除单个值，您如何定义要删除的值？
The reason you don't get a key back when querying on values is because the dictionary could contain multiple keys paired with the specified value.
查询值时没有取回键的原因是字典可能包含与指定值配对的多个键。
If you wish to remove all matching instances of the same value, you can do this:
如果您希望删除具有相同值的所有匹配实例，您可以这样做：
foreach(var item in dic.Where(kvp => kvp.Value == value).ToList())
{
dic.Remove(item.Key);
}
And if you wish to remove the first matching instance, you can query to find the first item and just remove that:
如果你想删除第一个匹配的实例，你可以查询找到第一项并删除它：
var item = dic.First(kvp => kvp.Value == value);
dic.Remove(item.Key);
Note:The ToList()call is necessary to copy the values to a new collection. If the call is not made, the loop will be modifying the collection it is iterating over, causing an exception to be thrown on the next attempt to iterate after the first value is removed.
注：该ToList()调用是必要的值复制到一个新的集合。如果未进行调用，循环将修改它正在迭代的集合，导致在删除第一个值后下次尝试迭代时抛出异常。
回答by Xinus
Loop through the dictionary to find the index and then remove it.
遍历字典以查找索引，然后将其删除。
回答by Amy B
Dictionary<string, string> source
//
//functional programming - do not modify state - only create new state
Dictionary<string, string> result = source
.Where(kvp => string.Compare(kvp.Value, "two", true) != 0)
.ToDictionary(kvp => kvp.Key, kvp => kvp.Value)
//
// or you could modify state
List<string> keys = source
.Where(kvp => string.Compare(kvp.Value, "two", true) == 0)
.Select(kvp => kvp.Key)
.ToList();
foreach(string theKey in keys)
{
source.Remove(theKey);
}
回答by Jahongir Murtozayev
In my case I use this
在我的情况下，我使用这个
var key=dict.FirstOrDefault(m => m.Value == s).Key;
dict.Remove(key);
回答by ezolotko
Here is a method you can use:
这是您可以使用的方法：
public static void RemoveAllByValue<K, V>(this Dictionary<K, V> dictionary, V value)
{
foreach (var key in dictionary.Where(
kvp => EqualityComparer<V>.Default.Equals(kvp.Value, value)).
Select(x => x.Key).ToArray())
dictionary.Remove(key);
}
回答by shoushouleb86
You can use the following as extension method
您可以使用以下作为扩展方法
public static void RemoveByValue<T,T1>(this Dictionary<T,T1> src , T1 Value)
{
foreach (var item in src.Where(kvp => kvp.Value.Equals( Value)).ToList())
{
src.Remove(item.Key);
}
}
