The given key was not present in the dictionary Which key

Question

Is there a way to get the value of the given key in the following exception in C  in a way that affects all generic classes  I think this is a big miss in the exception description from Microsoft    The given key was not present in the dictionary     A better way would be    The given key      key ToString        was not present in the dictionary     Solutions might involve mixins or derived classes maybe

User · Answer

In the general case  the answer is No   However  you can set the debugger to break at the point where the exception is first thrown  At that time  the key which was not present will be accessible as a value in the call stack   In Visual Studio  this option is located here   Debug  rarr  Exceptions     rarr  Common Language Runtime Exceptions  rarr  System Collections Generic  There  you can check the Thrown box     For more specific instances where information is needed at runtime  provided your code uses IDictionary lt TKey  TValue gt  and not tied directly to Dictionary lt TKey  TValue gt   you can implement your own dictionary class which provides this behavior

User · Answer

If you want to manage key misses you should use TryGetValue  https   msdn microsoft com en-gb library bb347013 v vs 110  aspx  string value       if  openWith TryGetValue  tif   out value         Console WriteLine  For key     tif    value    0     value     else       Console WriteLine  Key     tif   is not found

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string Value   dic ContainsKey  Name     dic  Name      Required Name    With this code  we will get string data in  Value   If key  Name  exists in the dictionary  dic  then fetch this value  else returns  Required Name  string

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You can try this code   Dictionary lt string string gt  AllFields   new Dictionary lt string string gt       string value    AllFields TryGetValue key  out index    AllFields key    null     If the key is not present  it simply returns a null value

User · Answer

This exception is thrown when you try to index to something that isn t there  for example  Dictionary lt String  String gt  test   new Dictionary lt String String gt     test Add  quot Key1 quot   quot Value1 quot    string error   test  quot Key2 quot     Often times  something like an object will be the key  which undoubtedly makes it harder to get  However  you can always write the following  or even wrap it up in an extension method   if  test ContainsKey myKey      return test myKey   else    throw new Exception String Format  quot Key  0  was not found quot   myKey     Or more efficient  thanks to  ScottChamberlain  T retValue  if  test TryGetValue myKey  out retValue       return retValue  else    throw new Exception String Format  quot Key  0  was not found quot   myKey     Microsoft chose not to do this  probably because it would be useless when used on most objects  Its simple enough to do yourself  so just roll your own

[c#] The given key was not present in the dictionary. Which key?

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