excel - SpecialCells(xlCellTypeConstants) results unexpected result on just one cell as the base range -

to summarize: if base range of specialcells 1 cell, result of range.specialcells(xlcelltypeconstants, xlnumbers) yields not cell or nothing. supposed, specialcells should yield range inside object applied... or wrong?

i've "developed" little new excel book, show don't understand, follows:

1. created new excel book

2. filled a1:b3, follows:

        b   ...  1 1  12  2 2  22  3 3  32  . 

   all other cells of sheet untouched.

3. inside new module i've added following code:

   private sub test()      dim oset range, ospec range, oused range      worksheets("sheet1").activate      set oset = activesheet.range("a1:a1")     set ospec = oset.specialcells(xlcelltypeconstants, xlnumbers)     set oused = activesheet.usedrange      set oset = nothing     set ospec = nothing     set oused = nothing  end sub 

4. running subroutine, , stopping @ first range reset, yields:

   oset.address = "$a$1" ospec.address = "$a$1:$b$3" ' seems wrong; should "$a$1" ? oused.address = "$a$1:$b$3" 

5. having been changed value of a1 a, rerun sub, , stop @ same place, gives (consistently previous, shows works consequtively):

   oset.address = "$a$1" ospec.address = "$b$1","$a$2:$b$3" ' seems wrong; should ospec nothing ? oused.address = "$a$1:$b$3" 

6. however, resetting value of a1 original 1, changing range of first set operation in subroutine cell "a1" true range of cells "a1:a2", rerun sub, , stop @ place, gives different (and more expected) result:

   oset.address = "$a$1:$a$2" ospec.address = "$a$1:$a$2" ' oused.address = "$a$1:$b$3" 

i appreciate, if explain results. ahead.

this happening because in case of 1 cell, considers usedrange instead.
references:
1) super secret specialcells
2) using specialcells in excel vba

as helpful note, give wrapper function specialcells , helper method (in c#, not in vba):

    /// <summary>     /// <para>wrapper specialcells function.</para>     /// </summary>     /// <param name="inputrange"></param>     /// <param name="celltype"></param>     /// <returns></returns>     /// <remarks>throws null when there no cells in <paramref name="inputrange"/> corresponding <paramref name="celltype"/>, unlike specialcells throws exception</remarks>     public static range getrangespecialcells(this microsoft.office.interop.excel.range inputrange, xlcelltype celltype)     {         try         {             if (inputrange.cells.count == 1)             {                 if (celltype == xlcelltype.xlcelltypecomments)                 {                     if (inputrange.comment != null)                     {                         return inputrange;                     }                     else                     {                         return null;                     }                 }                 else if (celltype == xlcelltype.xlcelltypeformulas)                 {                     if (inputrange.hasformula == true)                     {                         return inputrange;                     }                     else                     {                         return null;                     }                 }                 else if (celltype == xlcelltype.xlcelltypeblanks)                 {                     if (string.isnullorempty(inputrange.value2) == true)                     {                         return inputrange;                     }                     else                     {                         return null;                     }                 }                 else if (celltype == xlcelltype.xlcelltypelastcell)                 {                     return inputrange;                 }                 else                 {                     // since inputrange has single cell, specialcells apply entire worksheet                     // range has cells worksheet (usedrange) of type provided: celltype                     range temp = inputrange.specialcells(celltype);                      // intersect range single cell (inputrange) above range                     range rangeoverlap = intersect(inputrange, temp);                      // if range single cell contained in intersection, cell of type xlcelltypeconstants                     if (rangeoverlap.count == inputrange.count && rangeoverlap.rows.count == inputrange.rows.count && rangeoverlap.columns.count == inputrange.columns.count)                     {                         return inputrange;                     }                     else                     {                         return null;                     }                 }             }             else             {                 return inputrange.specialcells(celltype);             }         }         catch (system.runtime.interopservices.comexception ex)         {             return null;         }     }       /// <summary>     /// <para>customized function intersection of 2 ranges (<paramref name="rangea"/> ∩ <paramref name="rangeb"/>)</para>     /// </summary>     /// <param name="rangea"></param>     /// <param name="rangeb"></param>     /// <returns>range corresponding intersection of 2 provided ranges</returns>     /// <remarks>this function returns null if of provided ranges null or malformed, unlike application.intersect throws exception</remarks>     public static range intersect(range rangea, range rangeb)     {         range rngintersect;         if (rangea == null)         {             rngintersect = null;         }         else if (rangeb == null)         {             rngintersect = null;         }         else if (rangea.worksheet != rangeb.worksheet)         {             rngintersect = null;         }         else         {             try             {                 rngintersect = globals.thisaddin.application.intersect(rangea, rangeb);             }             catch (exception ex)             {                 rngintersect = null;             }         }          return rngintersect;     }