public enum baseKey : uint
{
    HKEY_CLASSES_ROOT = 0x80000000,
    HKEY_CURRENT_USER = 0x80000001,
    HKEY_LOCAL_MACHINE = 0x80000002,
    HKEY_USERS = 0x80000003,
    HKEY_CURRENT_CONFIG = 0x80000005
}

(uint)Enum.Parse(typeof(baseKey), "HKEY_LOCAL_MACHINE")

uint key = 0;
string s = "HKEY_LOCAL_MACHINE";
try
{
   key = (uint)Enum.Parse(typeof(baseKey), s);
}
catch(ArgumentException)
{
   //unknown string or s is null
}

baseKey e;

if ( Enum.TryParse(s, out e) )
{
 ...
}

var value = (uint) Enum.Parse(typeof(baseKey), someString);