vb.net - Class 'System.DBNull' cannot be indexed because it has no default property -

private sub button1_click(byval sender system.object, byval e system.eventargs) handles button1.click         cn.open()         dim arrimage() byte         dim ms new memorystream()         if (pb1.image isnot nothing)             pb1.image.save(ms, pb1.image.rawformat)             arrimage = ms.getbuffer             ms.close()         end if         cmd             .connection = cn             .commandtext = "insert [example]([pname],[pic])values(@a2,@a1)"             .parameters.add("a0", oledbtype.varchar).value = tname.text             .parameters.add("a1", oledbtype.binary).value = iif(pb1.image isnot nothing, arrimage, dbnull.value())             .dispose()             .executenonquery()         end         cn.close()     end sub 

you have multiple issues in code. in order of appearance:

dont use getbuffer()

as noted on msdn, buffer can twice size of data in stream. bloat database needlessly nulls. use toarray() instead.

since images in db have converted , byte array, consider archiving images folder , store name in database. can prepend archive folder name load image quickly.

rather rawformat, encode jpeg.

use using blocks

anything has .dispose method needs disposed. apply oledbcommand object (memstream doesnt need disposed, implementaion detail).

using blocks incoporate dim, new , dispose in 1 handy, easy use block:

using foo new foobar()    ... end using 

the first line declares foo variable, , creates instance of foobar can use inside block. @ end, disposed of automatically.

don't use global dbcommand objects

your code not show cmd being declared or created, must form level object. don't that. there nothing reusable dbcommand object unless app 1 thing.

in code add 2 parameters. next time go use it, still have 2 , code add 2 more more sql query requires. in case, code disposes of it, that means next time go reference objectdisposedexception.

• as noted, code calls dispose before executenonquery crash - cant use disposed object.

dbnull.value not method

as compiler error, have this:

iif(pb1.image isnot nothing, arrimage, dbnull.value()) 

dbnull.value property, not method, parens not needed. also, should use "new" if operator rather old iif function. operator short-circuited part/clause not apply ignored:

' should evaluate data (arrimage) not source if(pb1.image isnot nothing, arrimage, dbnull.value)   ' no parens 

revamped code:

cn.open() dim arrimage() byte = nothing  if (pb.image isnot nothing)     using ms new memorystream()         pb.image.save(ms, imageformat.jpeg)         arrimage = ms.toarray()     end using end if  dim sql = "insert [example]([pname],[pic]) values (@a2,@a1)"  using cmd new oledbcommand(sql, cn)     cmd.parameters.add("a0", oledbtype.varchar).value = tname.text     if arrimage isnot nothing         cmd.parameters.add("a1", oledbtype.varbinary).value = arrimage      else         cmd.parameters.add("a1", oledbtype.varbinary).value = dbnull.value     end if     cmd.executenonquery() end using  cn.close() 

• since command object useless without both query , connection, prefer pass them in constructor. makes code shorter assures has needs
• connections ought created, used , disposed of each time
• it easy create handy extension method converting image byte array