我发现升级代码存储在以下注册表位置。
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UpgradeCodes
注册表项名称是升级代码，注册表项值名称是产品代码。我可以轻松提取这些值，但是代码以不同的格式存储。红圈为格式化后的升级码，蓝圈为在regedit.exe查看时格式化后的产品码。
连字符从Guid 中去除，然后完成一系列字符串反转。前 8 个字符被反转，然后是接下来的 4 个，然后是后面的 4 个，然后字符串的其余部分以 2 个字符为一组进行反转。通常在反转字符串时，我们需要注意确保正确处理控制和特殊字符（see Jon Skeet's aricle here），但在这种情况下，处理Guid 字符串时，我们可以确信字符串将被反转正确。
以下是我用来从注册表中提取已知产品代码的升级代码的完整代码。
internal static class RegistryHelper
{
private const string UpgradeCodeRegistryKey = @"SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UpgradeCodes";
private static readonly int[] GuidRegistryFormatPattern = new[] { 8, 4, 4, 2, 2, 2, 2, 2, 2, 2, 2 };
public static Guid? GetUpgradeCode(Guid productCode)
{
// Convert the product code to the format found in the registry
var productCodeSearchString = ConvertToRegistryFormat(productCode);
// Open the upgrade code registry key
var localMachine = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64);
var upgradeCodeRegistryRoot = localMachine.OpenSubKey(UpgradeCodeRegistryKey);
if (upgradeCodeRegistryRoot == null)
return null;
// Iterate over each sub-key
foreach (var subKeyName in upgradeCodeRegistryRoot.GetSubKeyNames())
{
var subkey = upgradeCodeRegistryRoot.OpenSubKey(subKeyName);
if (subkey == null)
continue;
// Check for a value containing the product code
if (subkey.GetValueNames().Any(s => s.IndexOf(productCodeSearchString, StringComparison.OrdinalIgnoreCase) >= 0))
{
// Extract the name of the subkey from the qualified name
var formattedUpgradeCode = subkey.Name.Split('\\').LastOrDefault();
// Convert it back to a Guid
return ConvertFromRegistryFormat(formattedUpgradeCode);
}
}
return null;
}
private static string ConvertToRegistryFormat(Guid productCode)
{
return Reverse(productCode, GuidRegistryFormatPattern);
}
private static Guid ConvertFromRegistryFormat(string upgradeCode)
{
if (upgradeCode == null || upgradeCode.Length != 32)
throw new FormatException("Product code was in an invalid format");
upgradeCode = Reverse(upgradeCode, GuidRegistryFormatPattern);
return Guid.Parse(upgradeCode);
}
private static string Reverse(object value, params int[] pattern)
{
// Strip the hyphens
var inputString = value.ToString().Replace("-", "");
var returnString = new StringBuilder();
var index = 0;
// Iterate over the reversal pattern
foreach (var length in pattern)
{
// Reverse the sub-string and append it
returnString.Append(inputString.Substring(index, length).Reverse().ToArray());
// Increment our posistion in the string
index += length;
}
return returnString.ToString();
}
}