No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http:// localhost' is therefore not allowed access.

AngularJS which calls an API- WebMethod for json data. When cross domain origin problem got this error:
Error: 
XMLHttpRequest cannot load api
 No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin '.....' is therefore not allowed access.

Solution: 

Add to web.config:

    <httpProtocol>

      <customHeaders>

        <add name="Access-Control-Allow-Origin" value="*" />

        <add name="Access-Control-Allow-Headers" value="Content-Type, accessToken, signedInUserId, x-requested-with" />

      </customHeaders>

    </httpProtocol>