Basically, you would do something like this:
SQL String:
"SELECT * FROM users where Username='" & txtUsername.Text &"' AND password='" & txtPassword.Text &"'"
If the above query returns 0 results, the username or password is invalid, if it returns a row (It should always only return 1 row) then the username and password are correct.
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Read this if you want to know how to get a correct reply for your question:
http://www.catb.org/~esr/faqs/smart-questions.html
^^Took that from planoie's profile^^
^^Modified text taken from gbianchi profile^^
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Technical Editor for:
Professional Search Engine Optimization with ASP.NET
http://www.wiley.com/WileyCDA/WileyT...470131470.html
Discussion:
http://p2p.wrox.com/topic.asp?TOPIC_ID=56429