Question

I have the following controls:

• textbox1 – this is where i type a message.
• listbox1 – this is where i display the messages.
• button1 – this is what posts my messages to the server.
• StatusStrip1.Title1 – this is where the current user’s title will go. (i.e: Administrator, manager… etc.)

I have a table on a MYSQL database called “messages” and a column called “message”. When i type something into textbox1 and click button1 i want to add a row to “messages” under the column “message” with the title and message as its value.(separated by a hyphen, dash, or other small delimiter)Then reload listbox1’s contents to show the new message.

so i want the final message to be something like:

Administrator – Hello World!

I currently have the following code:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim sqlpost As MySqlCommand = New MySqlCommand("INSERT INTO messages(message) VALUES(?name - ?message)"";", con)
    sqlpost.Parameters.AddWithValue("?name", Title2.Text)
    sqlpost.Parameters.AddWithValue("?message", TextBox1.Text)
    Try
        con.Close()
        con.Open()

        ' Sending message.
        If TextBox1.Text = "" Then
            MessageBox.Show("You forgot to type a message!")
        Else
            sqlpost.ExecuteNonQuery()

            ' Reloading messages.

            ListBox1.Items.Clear()
            reader = sqlmessages.ExecuteReader()
            While (reader.Read)
                ListBox1.Items.Add(reader.Item("message"))
                ListBox1.Items.Add("")

            End While
            reader.Close()
            con.Close()
            TextBox1.Text = ""
            Label4.Text = "Message Sent!"
            Timer2.Start()
        End If

    Catch myerror As MySqlException
        MessageBox.Show("Error sending message to server: " & myerror.Message)
    End Try

End Sub

I had it working before, but when i made changes to it, it came up with various sql statement syntax errors… (stuff like invalid truncated value of “Administrator”, or invalid DOUBLE value “hello”) and now it won’t even display any messages currently in the “messages” table…)

If anyone could tell me what i’m doing wrong, or a more efficient way of doing this then i would greatly appreciate it! Thanks!

Answer 1

One thing I see that looks incorrect is that you are using “?” for you parameter names in the query. The default character to use for parameter names is to start them with “@”. Although I think there’s a connection string option to use “?” as that is what was used in the older versions of the MySQL connector, but the current default is “@”. Also, there seems to be some problems with your command in general. You have:

Dim sqlpost As MySqlCommand = New MySqlCommand("INSERT INTO messages(message) VALUES(?name - ?message)"";", con)

it should probably be something more like

Dim sqlpost As MySqlCommand = New MySqlCommand("INSERT INTO messages(message) VALUES(@message);", con)

I fixed up the query a bit, and replaced the ? with @. You you can do the concatenation of name and message (as you cleared up in the comment) in VB, with some code such as this:

sqlpost.Parameters.AddWithValue("@message", Title2.Text & " - " & Title2.Text)

I also see that you are calling

sqlmessages.ExecuteReader()

but I don’t see where this is being initialized.