I have a client who has a requirement to validate users logging into my web application against his active directory using LDAP. In trying to connect using the DirectoryEntry and DirectorySearcher .NET classes, I can connect to his AD Server but not access it.

The client's AD server has an SSL Certificate for which he has given me a public key file but I don't know how to use this public key file in my C# code.

When I issue the connect command through code, I see, via Wireshark, my application sending the connection request. I then see the server responding with "Server Hello, Certificate, Certificate Request, Server Hello Done". Then my application never responds after that.

In using another application, written by somebody else for which I do not have code, I see the same request from the server and then see the application respond with "Certificate, Client Key Exchange" and then the application connects and runs.

With that said, my question then becomes, how can I get my C# application to load and send the key file I got from the client?