Metadata publishing for this service is currently disabled.

Reason 1:

In your web.config

<service name="A.B.C">

but your class is：

namespace A.B
{
    .....
    public class D : E
    {

Those names need to match! The name= attribute on the <service> tag in config must be exactly what your service class is called - fully qualified, including namespace - so in your case here, it should be:

<service name="A.B.D">

Reason 2:

Make sure Web.config have httpGetEnabled or httpsGenEnabled parameter in <serviceMetadata> tag.

<behaviors>
      <serviceBehaviors>
        <behavior>
          <!-- To avoid disclosing metadata information, set the values below to false before deployment -->
          <serviceMetadata httpGetEnabled="true"/>
          <!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->
          <serviceDebug includeExceptionDetailInFaults="false"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>