WCF: "serviceActivations could not be found"

If you received this kind of error:

The type 'WcfService1.Service1', provided as the Service attribute value in the ServiceHost directive, or provided in the configuration element system.serviceModel/serviceHostingEnvironment/serviceActivations could not be found.

It's trying to find Wcf1Service1.Service1. To change to your current service name, example:

public class TestService : IService1
    {
        public string GetData(int value)
        {
            return string.Format("You entered: {0}", value);
        }
    }

...from Solution Explorer, right-click Service1.svc, choose Open With..., select XML (Text) Editor, click OK, change this...

<%@ ServiceHost Language="C#" Debug="true" Service="WcfService1.Service1" CodeBehind="Service1.svc.cs" %>

...To:

<%@ ServiceHost Language="C#" Debug="true" Service="WcfService1.TestService" CodeBehind="Service1.svc.cs" %>