(C#) Revert to Default DNS Nameservers

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Demonstrates how to revert back to the default nameservers of the local system where your application is running.

Note: This example requires Chilkat v9.5.0.96 or later.

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// The only reason you would have to revert back to the local system's default nameservers
// is if your application had previously set different nameservers, and you wish to revert back.

// When your application starts, the DNS nameservers to be used are the default nameservers
// configured on the system where your application is running.

// There is one exception: Chilkat defaults to using the public Google nameservers (8.8.8.8 and 8.8.4.4) for
// Android applications. Reverting to the default nameservers would revert to the Google nameservers.

// However, Chilkat does not query the local system for the default nameservers unless Chilkat needs
// to do a DNS lookup and there not yet any DNS nameservers defined.  Thus technically, when your application
// starts, there are no default nameservers. They are auto-assigned when first needed.

// If your application explicitly defines DNS nameservers, such as by calling AddDefaultnamervers, or AddNameserver
// then Chilkat will not automatically auto-assign.

Chilkat.Dns dns = new Chilkat.Dns();

// Here we are explicitly adding the system default nameservers, because technically this application
// has not yet done anything that would require a DNS lookup, and thus DNS nameservers are not yet defined.
// Your default nameserver is assumed to not support TLS.
dns.AddDefaultNameservers();

// Let's examine our nameservers
int nsCount = dns.NumNameservers;
int i = 0;
while (i < nsCount) {
    Debug.WriteLine(Convert.ToString(i + 1) + ": " + dns.GetNameserver(i));
    i = i + 1;
}

// On my Windows system, the result is a single nameserver at 
// 1: 172.16.16.16

// ---------------------------------------------------------
// We could add additional nameservers, such as Google and Cloudfare
bool supportsTls = true;
// Cloudfare
dns.AddNameserver("1.1.1.1",supportsTls);
// Google
dns.AddNameserver("8.8.8.8",supportsTls);

// See the nameservers now used by Chilkat
nsCount = dns.NumNameservers;
i = 0;
while (i < nsCount) {
    Debug.WriteLine(Convert.ToString(i + 1) + ": " + dns.GetNameserver(i));
    i = i + 1;
}

// Result:
// 1: 172.16.16.16
// 2: 1.1.1.1
// 3: 8.8.8.8

// ---------------------------------------------------------
// To revert back to the system default nameservers, clear all
// then re-add the default.
dns.RemoveAllNameservers();
dns.AddDefaultNameservers();

// See the nameservers now used by Chilkat
nsCount = dns.NumNameservers;
i = 0;
while (i < nsCount) {
    Debug.WriteLine(Convert.ToString(i + 1) + ": " + dns.GetNameserver(i));
    i = i + 1;
}

// Result:
// 1: 172.16.16.16