System.InvalidOperationException: Sequence contains no elements

Problem When you call .First() on an empty IEnumerable, you get the following exception: System.InvalidOperationException: Sequence contains no elements Solution Option 1 – Use .FirstOrDefault() instead of .First() When the IEnumerable is empty, .FirstOrDefault() returns the default value for the type. For reference types this returns null. For value types this returns 0 or that … Read more System.InvalidOperationException: Sequence contains no elements

KeyNotFoundException: The given key was not present in the dictionary

Problem The following exception is thrown when you try to get a value from a dictionary using a key that doesn’t exist in the dictionary: KeyNotFoundException: ‘The given key was not present in the dictionary.’ Consider the following the example: When the user enters a city name that isn’t in the dictionary, such as “New … Read more KeyNotFoundException: The given key was not present in the dictionary