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i am very new to coding and im trying to make my delete button work on my dataGridView so i can delete rows on sql


Private Sub BtnDelete_Click(sender As Object, e As EventArgs) Handles BtnDelete.Click
If (ValidateChildren(ValidationConstraints.Enabled)) Then
sqlQuery = "UPDATE TblLockerDGV SET STATUS = 'd' WHERE ID = " & RecordID

cmd.Connection = dbConn
cmd.CommandText = sqlQuery
Dim rowsAffected As Integer = cmd.ExecuteNonQuery()

If (rowsAffected > 0) Then
Me.InitiateLockerDGVTab()
MessageBox.Show("action performed succesfully!")
Else
MessageBox.Show("Action Failed.")
End If

End If
End Sub

What I have tried:

i am very new to coding and im trying to make my delete button work on my dataGridView so i can delete rows on sql


Private Sub BtnDelete_Click(sender As Object, e As EventArgs) Handles BtnDelete.Click
If (ValidateChildren(ValidationConstraints.Enabled)) Then
sqlQuery = "UPDATE TblLockerDGV SET STATUS = 'd' WHERE ID = " & RecordID

cmd.Connection = dbConn
cmd.CommandText = sqlQuery
Dim rowsAffected As Integer = cmd.ExecuteNonQuery()

If (rowsAffected > 0) Then
Me.InitiateLockerDGVTab()
MessageBox.Show("action performed succesfully!")
Else
MessageBox.Show("Action Failed.")
End If

End If
End Sub
Posted
Updated 28-May-21 9:26am

1 solution

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:
SQL
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:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'
Which SQL sees as three separate commands:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
SQL
DROP TABLE MyTable;
A perfectly valid "delete the table" command
SQL
--'
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?

Fix that throughout your app, and the chances are your error will disappear at the same time.
   
Comments
jsc42 28-May-21 17:43pm
   
What is the value in RecordID when the query is created? What creates it / updates it?
Have you tried stepping through the code and looking at the contents of the variables?

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