guessin game c#

PM> Install-Package NetSpell
Then, loop through the words and check them using the library
NetSpell.SpellChecker.Dictionary.WordDictionary oDict = new NetSpell.SpellChecker.Dictionary.WordDictionary();
oDict.DictionaryFile = "en-US.dic";
oDict.Initialize();
string wordToCheck = "Cat";
NetSpell.SpellChecker.Spelling oSpell = new NetSpell.SpellChecker.Spelling();
oSpell.Dictionary = oDict;
if(!oSpell.TestWord(wordToCheck))
{
//Word does not exist in dictionary
...
}

You can use NetSpell from Nuget to check any word .