Ive'd been getting an error "system.invalidoperationexception: the selectcommand property has not been initialized before calling 'fill'."

Question

1.00/5 (1 vote)

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This is my code:

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        openCon()
        MsgBox()
        con.Close()
        loadTable()
    End Sub

    Private Sub Button_add_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button_add.Click
        openCon()

        Try
            cmd.Connection = con
            cmd.CommandText = "INSERT INTO products (`ID`,`NAME`,`PRICE`,`QUANTITY`,`DESCRIPTION`) VALUES (" & TextBox_pID.Text & ",'" & TextBox_pName.Text & "'," & TextBox_pPrice.Text & "," & TextBox_pQty.Text & ",'" & TextBox_pDesc.Text & "')"
            cmd.ExecuteNonQuery()

            MsgBox("Product Successfully Added!")
            con.Close()
            
            TextBox_pID.Clear()
            TextBox_pName.Clear()
            TextBox_pPrice.Clear()
            TextBox_pQty.Clear()
            TextBox_pDesc.Clear()

            loadTable()

        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub

    Private Sub TextBox_pID_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox_pID.TextChanged
        openCon()

        Try
            cmd.Connection = con
            cmd.CommandText = "SELECT * FROM products WHERE ID='" & TextBox_pID.Text & "'"
            adapter.SelectCommand = cmd
            data.Clear()
            adapter.Fill(data, "List")

            TextBox_pName.DataBindings.Add("Text", data, "List.NAME")
            TextBox_pName.DataBindings.Clear()

            If TextBox_pID.Text = "" Then
                TextBox_pName.Clear()
            End If

            con.Close()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub

    Sub loadTable()
        openCon()

        Try
            cmd.Connection = con
            cmd.CommandText = "SELECT * FROM products"
            adapter.SelectCommand = cmd
            table.Clear()
            adapter.Fill(table)
            DataGridView1.DataSource = table
            con.Close()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub

End Class

I'm Using Visual Basic 2010 Express

Plss Help! Thanks!

What I have tried:

I have tried Changing the Values but nothing happend

Posted 18-May-22 17:35pm

Justin David Sanduco

Updated 18-May-22 19:09pm

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OriginalGriff · Answer 1 · 2022-05-18T19:09:00

First off, 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:

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?

When you have fixed that through your whole app, use the debugger to locate exactly where the problem occurs - there are a couple of Fills in thet code, and I can't see anything wrong with either (other than the recycling Connection and Adapters) so you need to find the actual code that causes the problem and look at what is and isn't setup with it - which needs you code running with your DB and we have no access to either!