Does anyone have an example of generating a signature for Oauth 1.0 in c#?

using restsharp is a solid choice

RestSharp is definitely a good choice, just note that the OAuth1Authenticator signature method defaults to HMAC-SHA1, so you need to override that to HMAC-SHA256 as in this example. The Realm also needs to be set on the OAuth1Authenticator instance to your account id.