Error when use INSERT from VB2005 to MySQL

[kikunosuke]

first, i am sorry if i can't speak english well

i have problem where i can't insert data to data base mySQl using vb2005.
it is my simple code on vb.

----------------------------------

Imports MySql.Data
Imports MySql.Data.MySqlClient

Public Class Form1
    Dim xobjConnection As New MySqlConnection("Server=localhost;uid=root;pwd=;database=test1;")

    Dim xobjAdapter As New MySqlDataAdapter()
    Dim xobjDataSet As DataSet


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim nim As String
        Dim nama As String

        nim = Me.TextBox1.Text
        nama = Me.TextBox2.Text

        Dim xobjCommand As MySqlCommand = New MySqlCommand()

        xobjCommand.Connection = Me.xobjConnection
        xobjCommand.CommandText = "INSERT INTO apple " & _
        "( nama, nim ) " & _
        "VALUES ( @nama, @nim)"

        xobjCommand.Parameters.AddWithValue("@nim", nim)
        xobjCommand.Parameters.AddWithValue("@nama", nama)

        Me.xobjConnection.Open()
        Try
            xobjCommand.ExecuteNonQuery()
        Catch mySqlExceptionErr As MySqlException
            MessageBox.Show(mySqlExceptionErr.Message)
        End Try
        Me.xobjConnection.Close()

    End Sub
End Class
--------------------------------

the message of this error is "column nim cannot be null"

//  i use 2 input box, and 1 button.
//  use phptriad. 
//  database = test1
// database = apple -> table = apple
// database = apple -> table = apple -> field = nim (varchar) primary key
                                                      -> field = nama (varchar) not primary key

// i used the newst mySQL_ connector  
// used visualstudio2005

Please help me.
sorry, and thanks (n_n)

[asnider]

Try using the following:

If nim = vbnullstring Then
                xobjCommand.Parameters.AddWithValue("@nim", dBNull.Value)
            Else
                xobjCommand.Parameters.AddWithValue("@nim", nim)
            End If

[kikunosuke]

hemm. it dosen't work..
the message error still same "column nim cannot be null"

...
i have try to check the 'nim' and 'nama'
//using
msgbox (nim) // and
msgbox (nama)

and put that syntax above
Me.xobjConnection.Open()

and the output of msgbox is same with what i have write on 'textbox'
so nim and nama wasn't null

[@bhi]

The problem seems to be that the values are not being set. Try this alternate method its basically doing the same thing:

xobjCommand.Parameters.Add("@nim",varchar)
xobjCommand.Parameters.Add("@nama",varchar)

xobjCommand.Parameters("@nim").value=nim
xobjCommand.Parameters("@nama").value=nama

[kikunosuke]

when i use that
there are message error
'Parameter '@nim' not found in the collection'