WCF Web服务找不到引用默认协定的端点元素

Question

我有一台有两项服务的服务器：

1. ContactService与IContactService和
2. SessionService与ISessionService

执行时出错：

  

“Impossible de trouverunééédedede point de terminaisonpardéfautquifaitréférenceaucontrat   'SessionServiceReference.ISessionService'用于配置客户端ServiceModel。   Cecipeutêtredûaufait que le fichier de configuration de votre application est introuvable ou   que l'élémentdepoint de terminaisonCorresponantàcecontrat est introuvable dans l'élémentclient。“

我的web.config：

<?xml version="1.0"?>
<configuration>

  <system.web>
    <authentication mode="Windows"/>
    <compilation debug="true" targetFramework="4.0" />
  </system.web>
  <system.serviceModel>
    <bindings>
      <customBinding>
        <binding name="InstantMessagingBinding" closeTimeout="00:10:00">
          <textMessageEncoding>
            <readerQuotas maxStringContentLength="200000" maxArrayLength="200000" />
          </textMessageEncoding>
          <httpTransport keepAliveEnabled="false" maxReceivedMessageSize="200000" authenticationScheme="Ntlm"/>
        </binding>
      </customBinding>
    </bindings>
    <behaviors>
        <serviceBehaviors>
            <behavior name="InstantMessagingBehavior">
                <serviceMetadata httpGetEnabled="true" />
                <serviceDebug includeExceptionDetailInFaults="true" />
            </behavior>
            <behavior name="">
                <serviceMetadata httpGetEnabled="true" />
                <serviceDebug includeExceptionDetailInFaults="false" />
            </behavior>
        </serviceBehaviors>
    </behaviors>
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true" />
    <services>
      <service name="Isima.InstantMessaging.WcfService.ContactService" behaviorConfiguration="InstantMessagingBehavior">
        <endpoint address=""
          binding="customBinding" bindingConfiguration="InstantMessagingBinding"
          contract="Isima.InstantMessaging.WcfService.IContactService" >
          <identity>
            <dns value="localhost" />
          </identity>
        </endpoint>
      </service>
      <service name="Isima.InstantMessaging.WcfService.SessionService" behaviorConfiguration="InstantMessagingBehavior">
        <endpoint address=""
          binding="customBinding" bindingConfiguration="InstantMessagingBinding"
          contract="Isima.InstantMessaging.WcfService.ISessionService" >
          <identity>
            <dns value="localhost" />
          </identity>
        </endpoint>
      </service>
    </services>
  </system.serviceModel>
 <system.webServer>
    <modules runAllManagedModulesForAllRequests="true"/>
  </system.webServer>

</configuration>

和app.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
    <bindings>
      <customBinding>
        <binding name="CustomBinding_IContactService">
          <textMessageEncoding />
          <httpTransport authenticationScheme="Ntlm" />
        </binding>
        <binding name="CustomBinding_ISessionService">
          <textMessageEncoding />
          <httpTransport authenticationScheme="Ntlm" />
        </binding>
      </customBinding>
    </bindings>
    <client>
      <endpoint address="http://localhost:2984/ContactService.svc"
        binding="customBinding" bindingConfiguration="CustomBinding_IContactService"
        contract="ContactServiceReference.IContactService" name="CustomBinding_IContactService">
        <identity>
          <dns value="localhost" />
        </identity>
      </endpoint>
      <endpoint address="http://localhost:2984/SessionService.svc"
        binding="customBinding" bindingConfiguration="CustomBinding_ISessionService"
        contract="SessionServiceReference.ISessionService" name="CustomBinding_ISessionService">
        <identity>
          <dns value="localhost" />
        </identity>
      </endpoint>
    </client>
  </system.serviceModel>
</configuration>

为什么会出现此错误？