how to convert a string to a bool

Quite simple indeed:

bool b = str == "1";

Ignoring the specific needs of this question, and while its never a good idea to cast a string to a bool, one way would be to use the ToBoolean() method on the Convert class:

bool val = Convert.ToBoolean("true");

or an extension method to do whatever weird mapping you're doing:

public static class StringExtensions
{
    public static bool ToBoolean(this string value)
    {
        switch (value.ToLower())
        {
            case  "true":
                return true;
            case "t":
                return true;
            case "1":
                return true;
            case "0":
                return false;
            case "false":
                return false;
            case "f":
                return false;
            default:
                throw new InvalidCastException("You can't cast that value to a bool!");
        }
    }
}