I am trying to validate credential for principal context using below code. But it is giving error "the server cannot handle directory requests".
principalContext.ValidateCredentials("Username", "Password");
After doing some internet search I came to know that I need to pass another parameter ContextOptions to make it work.
I found this link to resolve issue
.Net's Directory Services throws a strange exception
principalContext.ValidateCredentials("Username", "Password", ContextOptions.Negotiate);
It is working. But I cannot understand the root cause. If anyone can explain it in detail then it will be very helpful.