/// <summary>
/// Extracts information from a patch that can be used to determine whether the patch
/// applies on a target system. The method returns an XML string that can be provided to
/// <see cref="DetermineApplicablePatches(string,string[],InapplicablePatchHandler,string,UserContexts)"/>
/// instead of the full patch file.
/// </summary>
/// <param name="patchPath">Full path to the patch being queried.</param>
/// <returns>XML string containing patch data.</returns>
/// <remarks><p>
/// Win32 MSI API:
/// <a href="http://msdn.microsoft.com/library/en-us/msi/setup/msiextractpatchxmldata.asp">MsiExtractPatchXMLData</a>
/// </p></remarks>
public static string ExtractPatchXmlData(string patchPath)
{
StringBuilder buf = new StringBuilder("");
uint bufSize = 0;
uint ret = NativeMethods.MsiExtractPatchXMLData(patchPath, 0, buf, ref bufSize);
if (ret == (uint)NativeMethods.Error.MORE_DATA)
{
buf.Capacity = (int)++bufSize;
ret = NativeMethods.MsiExtractPatchXMLData(patchPath, 0, buf, ref bufSize);
}
if (ret != 0)
{
throw InstallerException.ExceptionFromReturnCode(ret);
}
return(buf.ToString());
}