best way to convert collection to string

I need to convert a collection of to a single string containing all the values in the collection like KeyValueKeyValue... But How do I do this effectively?

I have done it this way at the moment:

parameters = string.Join("", requestParameters.Select(x => string.Concat(x.Key, x.Value)));

But not sure it is the best way to do it, would a string builder be better? I guess the collection will contain a max of 10 pairs.