Getting "Object is read only" error when setting ClientCredentials in WCF

Question

I have a proxy object generated by Visual Studio (client side) named ServerClient. I am attempting to set ClientCredentials.UserName.UserName/Password before opening up a new connection using this code:

InstanceContext context = new InstanceContext(this);  m_client = new ServerClient(context); m_client.ClientCredentials.UserName.UserName = "Sample"; 

As soon as the code hits the UserName line it fails with an "Object is read-only" error. I know this can happen if the connection is already open or faulted, but at this point I haven't called context.Open() yet.

I have configured the Bindings (which uses netTcpBinding) to use Message as it's security mode, and MessageClientCredentialType is set to UserName.

Any ideas?

Answer 1

I noticed that after creating an instance of the proxy class for the service, I can set the Username and Password once without errors and do a successful call to my webservice. When I then try to set the Username and Password again on the existing instance (unnecessary of course) I get the 'Object is Read-Only' error you mentioned. Setting the values once per instance lifetime worked for me.

Answer 2

It appears that you can only access these properties pretty early in the instanciation cycle. If I override the constructor in the proxy class (ServerClient), I'm able to set these properties:

base.ClientCredentials.UserName.UserName = "Sample"; 

I'm beginning to appreciate the people who suggest not using the automatically built proxies provided by VS.