How to create and go to MVC endpoint with Javascript

Hi:

I have an MVC app in which I am doing a lookup in javascript and would like the program to take me to the following endpoint:

http://localhost:44328/Admin/ManageUsers/UserDetails/?username=jsmith

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I have a have a javascript function that looks like this:

 window.SalesHub.SearchBox_Select = function(e) {
        var baseUrl = 'http://localhost:44328';
        var actionUrl = '/Admin/ManageUsers/UserDetails/\?username=';
        var userName = 'jsmith';
        window.location.pathname = baseUrl + actionUrl + userName ;
}

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My problem is that this function takes me to:

http://localhost:44328/Admin/ManageUsers/UserDetails/%3Fusername=jsmith

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and tells me that "A potentially dangerous Request.Path value was detected from the client"

I have tried escaping the '?' character but that does not seem to work.  Any assistance on how to make this function take me to the endpoint that I want to go to greatly appreciated..

RBS