By wrapping the declarations for col1/col2 within quotes; you are making them strings of the content inside.
Furthermore, col2 is made up of a numeric function; and needs to be converted to a string. Try these replacements out
string col1 = cust_name;
string col2 = (tot_amt + adl_amt + tax_amt).ToString();
Console.WriteLine(col1);
Console.WriteLine(col2);
If you wanted to create a Class for this (eg Customer), you could do it similar to this
public class Customer {
public string cust_name { get; set; }
public int tot_amt { get; set; }
public int adl_amt { get; set; }
public int tax_amt { get; set; }
public Customer() {}
public string col1 { get { return cust_name; }}
public string col2 = {get {return (tot_amt+adl_amt+tax_amt).ToString(); }}
}
public cust = new Customer();
cust.cust_name = "Kishor";
cust.tot_amt = 100;
cust.adl_amt = 50;
cust.tax_amt = 18;
Console.WriteLine(col1);
Console.WriteLine(col2);
Or you could also create one with an overloaded construct like this to simplify the usage
public class Customer {
public string cust_name { get; set; }
public int tot_amt { get; set; }
public int adl_amt { get; set; }
public int tax_amt { get; set; }
public Customer() {}
public Customer(string nameCust, int amtTot, int amtAdl, int amtTax) {
cust_name = nameCust;
tot_amt = amtTot;
adl_amt = amtAdl;
tax_amt = amtTax;
}
public string col1 { get { return cust_name; }}
public string col2 = {get {return (tot_amt+adl_amt+tax_amt).ToString(); }}
}
public cust = new Customer("Kishor", 100, 50, 18);
Console.WriteLine(col1);
Console.WriteLine(col2);