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Editorial Team
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Asked: 2026-05-15T03:02:00+00:00

I am attempting to insert a custom behavior into my service client, following the

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I am attempting to insert a custom behavior into my service client, following the example here.

I appear to be following all of the steps, but I am getting a ConfigurationErrorsException. Is there anyone more experienced than me who can spot what I’m doing wrong?

Here is the entire app.config file.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.serviceModel>
        <behaviors>
            <endpointBehaviors>
                <behavior name="ClientLoggingEndpointBehaviour">
                    <myLoggerExtension />
                </behavior>
            </endpointBehaviors>
        </behaviors>
        <extensions>
            <behaviorExtensions>
                <add name="myLoggerExtension"
                     type="ChatClient.ClientLoggingEndpointBehaviourExtension, ChatClient, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null"/>
            </behaviorExtensions>
        </extensions>
        <bindings>
        </bindings>
        <client>
            <endpoint
                behaviorConfiguration="ClientLoggingEndpointBehaviour"
                name="ChatRoomClientEndpoint"
                address="http://localhost:8016/ChatRoom"
                binding="wsDualHttpBinding"
                contract="ChatRoomLib.IChatRoom"
                />
        </client>
    </system.serviceModel>
</configuration>

Here is the exception message:

An error occurred creating the
configuration section handler for
system.serviceModel/behaviors:
Extension element ‘myLoggerExtension’
cannot be added to this element.
Verify that the extension is
registered in the extension collection
at
system.serviceModel/extensions/behaviorExtensions.
Parameter name: element (C:\Documents
and Settings\Andrew Shepherd\My
Documents\Visual Studio
2008\Projects\WcfPractice\ChatClient\bin\Debug\ChatClient.vshost.exe.config
line 5)

I know that I’ve correctly written the reference to the ClientLoggingEndpointBehaviourExtensionobject, because through the debugger I can see it being instantiated.

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1 Answer

  1. Editorial Team

    It turns out that I didn’t get the assembly qualified name EXACTLY right.
    The assembly qualified name was correct enough for the .NET framework to load, but then the WCF framework performs a naive character-by-character comparison when matching the behavior configurations.

    To finally get the exact type name, I wrote code to create an instance of ClientLoggingEndpointBehaviourExtension object, and wrote the AssemblyQualifiedName property to a local variable, which I then copy-and-pasted from the debug window into the .config file.

    That I had to do all this is considered to be a bug in the WCF framework.
    (See this link)
    Apparently it’s fixed in .NET 4.0.

    Also see this article.

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