conn.ConnectionString = myConnString

mycommand.Connection = conn

If cboMessage.SelectedIndex -1 Then
myMessage = CType(cboMessage.SelectedItem, clsMessage)
Else
mycommand.CommandText = “Insert Into status(user_id, message,deleted) Values(?userID, ?message, ‘False’);” _
& “Select Last_Insert_ID()”
mycommand.Parameters.AddWithValue(“?userID”, myUserID)
mycommand.Parameters.AddWithValue(“?message”, cboMessage.Text)

Try
conn.Open()
myMessage = New clsMessage(mycommand.ExecuteScalar(), cboMessage.Text)
cboMessage.Items.Insert(1, myMessage)
cboMessage.SelectedIndex = 1
conn.Close()
Catch myerror As MySqlException
MsgBox(“There was an error updating the database:” & myerror.Message)
End Try
End If

mycommand.CommandText = “Insert into event(user_id, message_id, timestamp, status,creator)” _
& “Values(?UserID, ?MessageID, NOW(), ?Status, ?Creator)”
mycommand.Parameters.AddWithValue(“?UserID”, myUserID)

If myMessage.ID = -1 Then
mycommand.Parameters.AddWithValue(“?MessageID”, DBNull.Value)
Else
mycommand.Parameters.AddWithValue(“?MessageID”, myMessage.ID)
End If
mycommand.Parameters.AddWithValue(“?Status”, cboStatus.SelectedItem)
mycommand.Parameters.AddWithValue(“?Creator”, myUserID)

Try
conn.Open()
mycommand.ExecuteNonQuery()
Catch myerror As MySqlException
MsgBox(“There was an error updating the database:” & myerror.Message)
End Try
refreshStatus(dgvStatus)
End Sub

For the code “If myMessage.ID = -1 Then”, there is a blue line under the word myMessage.ID.
The warning said that: Variable ‘myMessage’ is used before it has been assigned a value. A null reference exception could result at runtime.

i am using visual studio2010 to do this.

does anyone can tell me what go wrong actually?
thanks

This is the duplicate line of code which caused the form to refuse personally specified messages being updated:

Extract from “the completed cmdUpdate_Click procedure” at end of tutorial 4.

>> myCommand.Parameters.Add(“?userID”, myUserID)
myCommand.Parameters.Add(“?message”, cboMessage.Text)

Try
conn.Open()
myMessage = New clsMessage(myCommand.ExecuteScalar(), cboMessage.Text)
cboMessage.Items.Insert(1, myMessage)
cboMessage.SelectedIndex = 1
conn.Close()
Catch myerror As MySqlException
MsgBox(“There was an error updating the database: ” & myerror.Message)
End Try
End If

myCommand.CommandText = “INSERT INTO event(user_id, message_id, timestamp, status, creator)” _
& “VALUES(?UserID, ?MessageID, NOW(), ?Status, ?Creator)”

>> myCommand.Parameters.Add(“?UserID”, myUserID)

The only difference between the above and my code is the “Add” becomes “AddWithValue” in VB 2008 Express

If anone can see how removing the “?” from “?UserID” may cause serious problems to the program down the line please let me and others who read this know. Thanks

und zwar habe ich folgendes problem: ich habe eine MySQL datenbank und möchte über VB.Net darauf zugreifen und bearbeiten aber es geht nicht ich bekomme keine verbindung zur datenbank. woran kann es liegen?

Public Function GetConnect()
Dim conn As New MySqlConnection

conn = New MySqlConnection(“server=localhost;user id=root;password=ariek;database=kartu_puas”)

Return conn

End Function

Private conn As New MySqlConnection(“server=localhost;user id=root;password=ariek;database=kartu_puas”)

Public MySqlComm As New MySql.Data.MySqlClient.MySqlCommand
Public Sub PerintahSQL(ByVal S As String)

MySqlComm = New MySql.Data.MySqlClient.MySqlCommand(S, conn)
MySqlComm.CommandType = CommandType.Text
MySqlComm.ExecuteNonQuery()
End Sub

Private Sub cbfakultas_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbfakultas.SelectedIndexChanged

Dim s As String = “SELECT * FROM jurusan where fakultas=’” & Me.cbfakultas.Text & “‘”
If conn.State = ConnectionState.Closed Then
conn = GetConnect()
conn.Open()
Else
conn = GetConnect()
conn.Close()
conn.Open()
End If

PerintahSQL(s)
Dim bb As MySql.Data.MySqlClient.MySqlDataReader = MySqlComm.ExecuteReader(CommandBehavior.CloseConnection)
Me.cbjurusan.Items.Clear()
Me.cbjurusan.Text = “”
Do While bb.Read

Me.cbjurusan.Items.Add(bb(“jurusan”))

Loop
conn = GetConnect()
conn.Close()
End Sub

its basically ‘key cannot be null. Parameter name : key’.
thats the error and all the syntax is exactly the same as the tutorial except i changed the query which works when typed into sql browser

I have the same problem with .Focus() method and solve it changing to .Select() method.