You have to close the quotes.
Did you read the previous answer.
if you're searching on a string the value must be entered between single quotes ,else no single quotes.

your string :
"SELECT * from birds1 where class no=txtvalue.text
if class no is a field name it should be placed between brakets.

so it would be for a text value in class no
"SELECT * from birds1 where [class no] = '" & txtvalue.text & "'"

and for a number in class no

"SELECT * from birds1 where class no= " & txtvalue.text

I hope this helps