c# - Return value using String result=Command.ExecuteScalar() error occurs when result returns null -

i want fetch 1st row 1st cell value database works below code . when there no result found throws exception.

how handle dbnull .
should change query ? return value if theirs no record ?

system.nullreferenceexception: object reference not set instance of object.

code:

    public string absentdayno(datetime sdate, datetime edate, string idemp)     {         string result="0";        string myquery="select count(idemp_atd) absentdayno td_atd ";        myquery +=" absentdate_atd between '"+sdate+"' , '"+edate+" ";        myquery +=" , idemp_atd='"+idemp+"' group idemp_atd ";         sqlcommand cmd = new sqlcommand(myquery, conn);        conn.open(); //system.nullreferenceexception occurs when no data/result        string getvalue = cmd.executescalar().tostring();          if (getvalue != null)          {             result = getvalue.tostring();          }          conn.close();         return result;     } 

there no need keep calling .tostring() getvalue string.

aside that, line possibly problem:

 string getvalue = cmd.executescalar().tostring();   

if there no rows .executescalar return null need checking.

for instance:

var firstcolumn = cmd.executescalar();  if (firstcolumn != null) {     result = firstcolumn.tostring(); }