set blank ip address or remove ip adddress

Question

I want to set ip address, subnet, gateway & dns; there is no issue in setting up but once the ip address is applied i'm trying to delete the existing gateway, pref dns its not working.

I tried to send a empty string but its always picking up .... (4dots) instead of empty string.

How can i set empty ip address or delete the gateway & pref dns ipaddress using the below method?

Get ip address from textbox usercontrol:

string[] pdns = ipsefpredns.GetIPaddress();
string str_pdns = pdns[0].ToString() + "." + pdns[1].ToString() + "." + pdns[2].ToString() + "." + pdns[3].ToString();
string ipaddressprefdns;
string emptypdns = pdns[0].ToString() + pdns[1].ToString()  + pdns[2].ToString()  + pdns[3].ToString(); 

if (pdns == null || pdns.Length ==0) //if the array is empty,null get empty string
{
    
    ipaddressprefdns = emptypdns;
    
}
else
{
    ipaddressprefdns = str_pdns;

}

Method to apply ipaddress:

string fileName = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "netsh");
Process.Start(new ProcessStartInfo(fileName)
{
    Arguments = string.Format("interface ip set address \"{0}\" static {1} {2} {3}", nicname, ipaddressstatic, ipaddresssubnet, ipaddressgateway),
    CreateNoWindow = true,
    WindowStyle = ProcessWindowStyle.Hidden
}).WaitForExit();
Process.Start(new ProcessStartInfo(fileName)
{
    Arguments = string.Format("interface ip set dns \"{0}\" static {1} Primary", nicname, ipaddressprefdns),
    CreateNoWindow = true,
    WindowStyle = ProcessWindowStyle.Hidden
}).WaitForExit();

Answer 1

I found a solution by reading the array then compare withit, pass none to gateway address.

string[] pdns = ipsefpredns.GetIPaddress();
string str_pdns = pdns[0].ToString() + "." + pdns[1].ToString() + "." + pdns[2].ToString() + "." + pdns[3].ToString();
string ipaddressprefdns="";
string prefdnss = UsingLoopStringBuilder(pdns);
if (!String.IsNullOrEmpty(prefdnss))
{
    ipaddressprefdns = str_pdns;
}
else
{
    ipaddressprefdns = "none";
}

//method to read string array[]
public string UsingLoopStringBuilder(string[] array)
{
    var result = new StringBuilder();
    foreach (var item in array)
    {
        result.Append(item);
    }
    return result.ToString();
}