Simple: don't do it like that. Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.
When you concatenate strings, you cause problems because SQL receives commands like:
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;
Which SQL sees as three separate commands:
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
DROP TABLE MyTable;
A perfectly valid "delete the table" command
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.
So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?
There are loads of other things which are badly done here: as Dave mentioned, using Form1 all the time is a bad idea, as is using a common Command object, the magic numbers in your access to the reader data, that you don't check any data is returned at all, ... Basically, wherever you copied that code from, he's an idiot who knows nothing about how to to code properly, and you would be a whole load better of just deleting his "code" and starting again from scratch.
This is a parameterised query done properly:
Using con As New SqlConnection(strConnect)
con.Open()
Using cmd As New SqlCommand("SELECT iD, description FROM myTable WHERE ProductName = @PRODNAME", con)
cmd.Parameters.AddWithValue("@PRODNAME", itemdesc)
Using reader As SqlDataReader = cmd.ExecuteReader()
While reader.Read()
Dim id__1 As Integer = CInt(reader("iD"))
Dim desc As String = DirectCast(reader("description"), String)
Console.WriteLine("ID: {0}" & vbLf & " {1}", iD, desc)
End While
End Using
End Using
End UsingNow use that pattern throughout your app - or lose your DB ...
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