/// <summary>
/// Enumerates patch installations based on certain criteria.
/// </summary>
/// <param name="patchCode">PatchCode (GUID) of the patch to be enumerated. Only
/// instances of patches within the scope of the context specified by the
/// <paramref name="userSid"/> and <paramref name="context"/> parameters will be
/// enumerated. This parameter may be set to null to enumerate all patches in the specified
/// context.</param>
/// <param name="targetProductCode">ProductCode (GUID) product whose patches are to be
/// enumerated. If non-null, patch enumeration is restricted to instances of this product
/// within the specified context. If null, the patches for all products under the specified
/// context are enumerated.</param>
/// <param name="userSid">Specifies a security identifier (SID) that restricts the context
/// of enumeration. A SID value other than s-1-1-0 is considered a user SID and restricts
/// enumeration to the current user or any user in the system. The special SID string
/// s-1-1-0 (Everyone) specifies enumeration across all users in the system. This parameter
/// can be set to null to restrict the enumeration scope to the current user. When
/// <paramref name="userSid"/> must be null.</param>
/// <param name="context">Specifies the user context.</param>
/// <param name="states">The <see cref="PatchStates"/> of patches to return.</param>
/// <remarks><p>
/// Win32 MSI APIs:
/// <a href="http://msdn.microsoft.com/library/en-us/msi/setup/msienumpatchesex.asp">MsiEnumPatchesEx</a>
/// </p></remarks>
public static IEnumerable <PatchInstallation> GetPatches(
string patchCode,
string targetProductCode,
string userSid,
UserContexts context,
PatchStates states)
{
StringBuilder buf = new StringBuilder(40);
StringBuilder targetProductBuf = new StringBuilder(40);
UserContexts targetContext;
StringBuilder targetSidBuf = new StringBuilder(40);
for (uint i = 0; ; i++)
{
uint targetSidBufSize = (uint)targetSidBuf.Capacity;
uint ret = NativeMethods.MsiEnumPatchesEx(
targetProductCode,
userSid,
context,
(uint)states,
i,
buf,
targetProductBuf,
out targetContext,
targetSidBuf,
ref targetSidBufSize);
if (ret == (uint)NativeMethods.Error.MORE_DATA)
{
targetSidBuf.Capacity = (int)++targetSidBufSize;
ret = NativeMethods.MsiEnumPatchesEx(
targetProductCode,
userSid,
context,
(uint)states,
i,
buf,
targetProductBuf,
out targetContext,
targetSidBuf,
ref targetSidBufSize);
}
if (ret == (uint)NativeMethods.Error.NO_MORE_ITEMS)
{
break;
}
if (ret != 0)
{
throw InstallerException.ExceptionFromReturnCode(ret);
}
string thisPatchCode = buf.ToString();
if (patchCode == null || patchCode == thisPatchCode)
{
yield return(new PatchInstallation(
buf.ToString(),
targetProductBuf.ToString(),
targetSidBuf.ToString(),
targetContext));
}
}
}