Remove Item in Dictionary based on Value

Question

I have a Dictionary lt string  string gt    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   ContainsValue just says true false and not the index or key of that item   Help   Thanks  EDIT  Just found this - what do you think   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  foreach  KeyValuePair lt string  string gt  kvp in myDic        if  myList Any x   gt  x Id    kvp Value           myDic Remove kvp Key

User · Answer

Loop through the dictionary to find the index and then remove it

User · Answer

Dictionary lt string  string gt  source      functional programming - do not modify state - only create new state Dictionary lt string  string gt  result   source    Where kvp   gt  string Compare kvp Value   two   true     0     ToDictionary kvp   gt  kvp Key  kvp   gt  kvp Value        or you could modify state List lt string gt  keys   source    Where kvp   gt  string Compare kvp Value   two   true     0     Select kvp   gt  kvp Key     ToList     foreach string theKey in keys      source Remove theKey

User · Answer

Are you trying to remove a single value or all matching values   If you are trying to remove a single value  how do you define the value you wish to remove   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   If you wish to remove all matching instances of the same value  you can do this   foreach var item in dic Where kvp   gt  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   var item   dic First kvp   gt  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

User · Answer

Here is a method you can use       public static void RemoveAllByValue lt K  V gt  this Dictionary lt K  V gt  dictionary  V value                foreach  var key in dictionary Where                  kvp   gt  EqualityComparer lt V gt  Default Equals kvp Value  value                    Select x   gt  x Key  ToArray                dictionary Remove key

User · Answer

You can use the following as extension method   public static void RemoveByValue lt T T1 gt  this Dictionary lt T T1 gt  src   T1 Value                foreach  var item in src Where kvp   gt  kvp Value Equals  Value   ToList                          src Remove item Key

User · Answer

In my case I use this    var key dict FirstOrDefault m   gt  m Value    s  Key              dict Remove key

[c#] Remove Item in Dictionary based on Value

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