Question

.Net core libraries source code (that can be accessed using Resharper) sometimes contain weird part “[….]” that you can see not only in comments, but in the code itself. What does it mean and why is it there?

From HttpWebRequest:

    // Return null only on [....] (if we're on the [....] thread).  Otherwise throw if no context is available.
    internal override ContextAwareResult GetConnectingContext() 
    {
        if (!Async)
        {
            GlobalLog.ThreadContract(ThreadKinds.User | ThreadKinds.[....], "HttpWebRequest#" + ValidationHelper.HashString(this) + "::GetConnectingContext"); 
            return null;
        } 

Answer 1

This is certainly not valid C# code. Keep in mind that Resharper is not the only tool to access the sources, you can also get them from the Microsoft Source Servers directly.

If you look at the same Method in ILSpy, you get to see this:

internal override ContextAwareResult GetConnectingContext()
{
    if (!this.Async)
    {
        return null;
    }

I would assume the GlobalLog.ThreadContract refers to a code contract that the team uses internally. The source might have simply been stripped in order to remove some sensitive internal information (although I cant imagine what this should be).