How to force ASP.NET Web API to return JSON or XML data based on my input?

Add the below code app_start event in global.asax file. In API Url add the query string:

GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(
    new QueryStringMapping("type", "json", new MediaTypeHeaderValue("application/json")));

GlobalConfiguration.Configuration.Formatters.XmlFormatter.MediaTypeMappings.Add(
    new QueryStringMapping("type", "xml", new MediaTypeHeaderValue("application/xml")));

e.g.:

for xml : http://localhost:49533/api/?type=xml

for json: http://localhost:49533/api/?type=json