可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试):

问题:

I am trying to add service reference.

There was an error downloading metadata from the address

this is the error which is being displayed again and again?

Please help

回答1:

There are atleast 4 possibilities:

The metadata exchange mex endpoint is not defined
metadata exchange is not enabled
You are using the wrong address
You are being blocked by some security setting

Try the url in a browser to see that it returns a wsdl

回答2:

You may also just need to build / rebuild the project.

回答3:

It was happening the same to me and I found that I've had forgotten to add the "Service Contract" and the "Operation Contract" annotations on the interface of my WCF service

回答4:

Just try to Build the project without any error and give service reference again.

回答5:

In Web.config file I changed :

 <endpoint address="" binding="pollingDuplexHttpBinding"
    contract="IAsyncTaskService"/>

to this :

<endpoint address="" binding="pollingDuplexHttpBinding"
    contract="DuplexService.Web.IAsyncTaskService"/>

and error was removed. Zeni

回答6:

Try rebuilding the project first, if that does not fix it, try changing the property httpGetEnabled from FALSE to TRUE in your web.config.

  <serviceBehaviors>
    <behavior name="serviceBehavior">
      <serviceMetadata httpGetEnabled="true"/>
      <serviceDebug includeExceptionDetailInFaults="false"/>
    </behavior>
  </serviceBehaviors>

回答7:

Another possibility in this situation is that there is no endpoint listening. I.e., the service you are trying to add isn't "up". I made this mistake when trying to add a reference to a WCF service I was working on, but I forgot to Open it.

回答8:

Check IIS is serving the service URL. In my case, I had changed my Windows password, but had forgotten that these credentials were being used by IIS in both the application and the app pool.

回答9:

I had an issue like this one : Adding a service reference failed with a message "Method not allowed".

The wsdl worked fine in my browser..

The reason was that I configured the endpoint to listen on http://0.0.0.0:6000/mex, which the "Add Service Reference" tool doesn't seem to like. Changing it to a real IP address made it work (e.g. http://127.0.0.1:6000/mex)