unable to read lookup column value in itemadded() event handler - object reference error

hi all,

 am working on a event receiver wherein i need to read a  look up column from the doc lib, the event reciver is fired correctly, [ itemadded eventhandler]  when i uploaded a  document from my custom web part.

after document is added into the document library along with few metadata columns -w hich contains lookup column, spfield choice, single line of text etc.. i have to read these columns and perform another logic.

but i am not able to read the lookup column .

can an one point me, whats i was missing . when i debugged the code,

if(mitem["mylookupcolumn"]  != null ) //here it throws object reference  error 

{ // my  logic }

 if (singleItem.Fields[mylookupcolumnname] is SPFieldLookup)

                {

                    SPFieldLookupValue spfieldLookUpValue = newSPFieldLookupValue(singleItem[mylookupcolumnname] as string); /// it thros the //error object reference error

                  selectedValue = spfieldLookUpValue.LookupValue.ToString();

                }

help is highly appreciated!

Das