Passing an array of values in Url.Action

I assume you "own" the controller? If so, I'd serialize and deserialize the list as a comma separated string on each side. It'd also be nice if criteria.JobTypes is an empty list instead of a possible null, then you don't need the ?? below.

var redirectUrl = Url.Action("search", new {
    // ...
    jobTypes = String.Join(criteria.JobTypes ?? new string[0], ",")
}

And do jobTypes.split(",") in the action.

URL would look a bit nicer too:

/search?q=developer&advanced=false&salaryfrom=20000&salaryto=80000&jobTypes=Full%20Time,Contract

To expand on Lars-Erik's answer, you can also use the other overload, the one that takes a dictionary.
This is also useful to construct e.g. an input that might or might not be disabled.

RouteValueDictionary args = new RouteValueDictionary {
    {"q", criteria.Q},
    {"advanced", criteria.Advanced},
    {"salaryfrom", criteria.SalaryFrom},
    {"salaryto", criteria.SalaryTo},
};
if(criteria.JobTypes != null) {
    // Either foreach the jobTypes or go Lars-Erik's way (nicer).
    args.Add("jobTypes", "foo");
}

Take care about special characters!
If you don't fully control the input, you might get a jobType "R&D" that will break your url: /search?q=...&jobTypes=R&D gets you jobTypes=R.

You can add the array elements individually to the RouteValueDictionary -- you just have to change the name to match the model binding name for round trip purposes.

The second argument to your action can be a RouteValueDictionary as ANeves said.

RouteValueDictionary rvd = new RouteValueDictionary { { "name", "value"}, ...};
int i = 0;
criteria.JobTypes.ForEach(v => rvd.Add(String.Format("jobTypes[{0}]", i++), (object) v));