Describe both the appropriate key fields and the appropriate value fields with classes. and use a dictionary of those types.
var dictionary = new Dictionary();
Note: If you have multiple values acting as the key, you would define a class to encapsulate those values and provide proper overrides of GetHashCode and Equals so that the dictionary could recognize their equality.
Short of doing this, you can utilize tuples, but you want to limit this pattern, as tuples are non self-describing.
var dictionary = new Dictionary, Tuple>();