c# - assigning a string to a string variable throwing Arithmetic operation resulted in an overflow, -

while processing following code getting error.

querycommand= "select user_name,user_lastname,user_address usertable" objodbcdatareader = dbconobject.getdatareader(querycommand) if objodbcdatareader.hasrows = true    dim username = objodbcdatareader.item("user_name").tostring() 'here throws error arithmetic operation resulted in overflow end if 

getdatareader method that accept query string , return result datareader.

let me know why error occurring while assigning string value string variable?

am using

visualstudio 2012 mysql 5.0 odbc driver 3.51 64 bit os 

in if statement testing see if rows exist,

at point have not read data?

querycommand= "select user_name,user_lastname,user_address usertable" objodbcdatareader = dbconobject.getdatareader(querycommand) if objodbcdatareader.hasrows = true   objodbcdatareader.read()   lsfinyear = objodbcdatareader.item("user_name") 'here throws error arithmetic operation resulted in overflow end if