private void ShowGroupInformation(Autodesk.Revit.DB.Document document, Autodesk.Revit.DB.Element element)
{
    // Get group information for the selected element
    String prompt = null;
    if (element.GroupId.Equals(ElementId.InvalidElementId))
    {
        prompt = "The element isn't in any group.";
    }
    else
    {
       Autodesk.Revit.DB.Group group = document.GetElement(element.GroupId) as Autodesk.Revit.DB.Group;

        prompt = "The element " + element.Id.IntegerValue + " is in a group.";
        prompt += "\nThe group id is " + group.Id.IntegerValue;
        prompt += "\nThe group's category is " + group.Category.Name;
        prompt += "\nAll group contained element ids are:";
        IList<ElementId> memberIds = group.GetMemberIds();
        foreach (ElementId id in memberIds)
        {
            prompt += "\n\t" + id.IntegerValue;
        }
    }

    TaskDialog.Show("Revit",prompt);
}

// Change the default group name to a new name �MyGroup�
group.GroupType.Name = "MyGroup";

public void GetInfo_Group(Group group)
{
    string message = "Group : ";

    // Show the group type name
    message += "\nGroup type name is : " + group.GroupType.Name;

    // Show the name of the elements contained in the group
    message += "\nThe members contained in this group are:";
    IList<ElementId> groupMembers = group.GetMemberIds();
    foreach (ElementId memberId in groupMembers)
    {

        message += "\n\tGroup member id : " + memberId.IntegerValue;
    }

    message += "\nAll member will now be removed from group.";
    group.UngroupMembers();

    TaskDialog.Show("Revit",message);
}

Private Sub ShowGroupInformation(document As Autodesk.Revit.DB.Document, element As Autodesk.Revit.DB.Element)
    ' Get group information for the selected element
    Dim prompt As [String] = Nothing
    If element.GroupId.Equals(ElementId.InvalidElementId) Then
        prompt = "The element isn't in any group."
    Else
        Dim group As Autodesk.Revit.DB.Group = TryCast(document.GetElement(element.GroupId), Autodesk.Revit.DB.Group)

        prompt = "The element " & Convert.ToString(element.Id.IntegerValue) & " is in a group."
        prompt += vbLf & "The group id is " + group.Id.IntegerValue
        prompt += vbLf & "The group's category is " + group.Category.Name
        prompt += vbLf & "All group contained element ids are:"
        Dim memberIds As IList(Of ElementId) = group.GetMemberIds()
        For Each id As ElementId In memberIds
            prompt += vbLf & vbTab + id.IntegerValue
        Next
    End If

    TaskDialog.Show("Revit", prompt)
End Sub

' Change the default group name to a new name �MyGroup�
group.GroupType.Name = "MyGroup"

Public Sub GetInfo_Group(group As Group)
    Dim message As String = "Group : "

    ' Show the group type name
    message += vbLf & "Group type name is : " & Convert.ToString(group.GroupType.Name)

    ' Show the name of the elements contained in the group
    message += vbLf & "The members contained in this group are:"
    Dim groupMembers As IList(Of ElementId) = group.GetMemberIds()
    For Each memberId As ElementId In groupMembers

        message += vbLf & vbTab & "Group member id : " + memberId.IntegerValue
    Next

    message += vbLf & "All member will now be removed from group."
    group.UngroupMembers()

    TaskDialog.Show("Revit", message)
End Sub