private bool CombineRevision(Document document, Revision revision)
{
    bool combined = false;
    // Can only combine two revisions if neither have been issued
    if (revision.Issued == false)
    {
        ElementId revisionId = revision.Id;
        Revision nextRevsion = GetNextRevision(document, revisionId);
        if (nextRevsion != null && nextRevsion.Issued == false)
        {
            ISet<ElementId> revisionCloudIds = Revision.CombineWithNext(document, revisionId);
            combined = true;
            int movedClouds = revisionCloudIds.Count;
            if (movedClouds > 0)
            {
                RevisionCloud cloud = document.GetElement(revisionCloudIds.ElementAt(0)) as RevisionCloud;
                if (cloud != null)
                {
                    string msg = string.Format("Revision {0} deleted and {1} revision clouds were added to Revsion {2}",
                        revisionId.ToString(), movedClouds, cloud.RevisionId.ToString());
                    TaskDialog.Show("Revision Combined", msg);
                }
            }
        }
    }

    return combined;
}

private Revision GetNextRevision(Document document, ElementId currentRevisionId)
{
    Revision nextRevision = null;
    IList<ElementId> revisionIds = Revision.GetAllRevisionIds(document);
    int currentRevisionIndex = -1;
    for (int n = 0; n < revisionIds.Count; n++)
    {
        if (revisionIds[n] == currentRevisionId)
        {
            currentRevisionIndex = n;
            break;
        }
    }

    // if the current revision id was found and is not the last index
    if (currentRevisionIndex >= 0 && currentRevisionIndex < revisionIds.Count - 1)
    {
        ElementId nextRevisionId = revisionIds[currentRevisionIndex + 1];
        nextRevision = document.GetElement(nextRevisionId) as Revision;
    }

    return nextRevision;
}

Private Function CombineRevision(document As Document, revision__1 As Revision) As Boolean
    Dim combined As Boolean = False
    ' Can only combine two revisions if neither have been issued
    If revision__1.Issued = False Then
        Dim revisionId As ElementId = revision__1.Id
        Dim nextRevsion As Revision = GetNextRevision(document, revisionId)
        If nextRevsion IsNot Nothing AndAlso nextRevsion.Issued = False Then
            Dim revisionCloudIds As ISet(Of ElementId) = Revision.CombineWithNext(document, revisionId)
            combined = True
            Dim movedClouds As Integer = revisionCloudIds.Count
            If movedClouds > 0 Then
                Dim cloud As RevisionCloud = TryCast(document.GetElement(revisionCloudIds.ElementAt(0)), RevisionCloud)
                If cloud IsNot Nothing Then
                    Dim msg As String = String.Format("Revision {0} deleted and {1} revision clouds were added to Revsion {2}", revisionId.ToString(), movedClouds, cloud.RevisionId.ToString())
                    TaskDialog.Show("Revision Combined", msg)
                End If
            End If
        End If
    End If

    Return combined
End Function

Private Function GetNextRevision(document As Document, currentRevisionId As ElementId) As Revision
    Dim nextRevision As Revision = Nothing
    Dim revisionIds As IList(Of ElementId) = Revision.GetAllRevisionIds(document)
    Dim currentRevisionIndex As Integer = -1
    For n As Integer = 0 To revisionIds.Count - 1
        If revisionIds(n) = currentRevisionId Then
            currentRevisionIndex = n
            Exit For
        End If
    Next

    ' if the current revision id was found and is not the last index
    If currentRevisionIndex >= 0 AndAlso currentRevisionIndex < revisionIds.Count - 1 Then
        Dim nextRevisionId As ElementId = revisionIds(currentRevisionIndex + 1)
        nextRevision = TryCast(document.GetElement(nextRevisionId), Revision)
    End If

    Return nextRevision
End Function