CODEWITHSUNDEEP
vb.netwinformsvisual-studiocombobox
user5520817
user5520817

Reputation:

Overwriting previous combobox selection?

I currently have two ComboBoxes in my form. ComboBox A is used for the selection of a certain item. ComboBox B will populate with 4 items that are specific to the selection that is made in ComboBox A. I was able to get all of that working.

My problem is: If I make a selection in ComboBox A, ComboBox B will populate with the 4 items specific to the selection I made in ComboBox A. But if I make another selection in ComboBox A, the items do not overwrite the previous items that were populated in ComboBox B, they are just added to the items that are already populated.

My question is, is there anyway to overwrite the previous itemsin ComboBox B when a new selection is made in ComboBox A?

Imports MySql.Data.MySqlClient
Public Class Form2
Dim MySqlConn As MySqlConnection
Dim COMMAND As MySqlCommand
Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    MySqlConn = New MySqlConnection
    MySqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=test"
    Dim READER As MySqlDataReader
    Try
        MySqlConn.Open()
        Dim Query As String
        Query = "select * from test.boxinformation"
        COMMAND = New MySqlCommand(Query, MySqlConn)
        READER = COMMAND.ExecuteReader
        While READER.Read
            Dim boxSN = READER.GetString("Box_SN")
            ComboBox_Box.Items.Add(boxSN)
        End While
        MySqlConn.Close()
    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        MySqlConn.Dispose()
    End Try
End Sub
Private Sub ComboBox_STSBox_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox_Box.SelectedIndexChanged
    MySqlConn = New MySqlConnection
    MySqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=test"
    Dim READER As MySqlDataReader
    Try
        MySqlConn.Open()
        Dim Query As String
        Query = "select * from test.boxinformation where Box_SN='" & ComboBox_Box.Text & "'"
        COMMAND = New MySqlCommand(Query, MySqlConn)
        READER = COMMAND.ExecuteReader
        While READER.Read
            ComboBox_Port.Items.Add(READER.GetString("1_IP"))
            ComboBox_Port.Items.Add(READER.GetString("2_IP"))
            ComboBox_Port.Items.Add(READER.GetString("3_IP"))
            ComboBox_Port.Items.Add(READER.GetString("4_IP"))
        End While
        MySqlConn.Close()
    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        MySqlConn.Dispose()
    End Try
End Sub

End Class

Upvotes: 0

Views: 129

Answers (2)

Shai Rado
Shai Rado

Reputation: 33682

In order to celan you ComboBox from previous values use ComboBox_Port.Clear , put it after your line 

READER = COMMAND.ExecuteReader

So your code will be:

READER = COMMAND.ExecuteReader
' *** drop your new line here ***
ComboBox_Port.Clear
While READER.Read
    ComboBox_Port.Items.Add(READER.GetString("1_IP"))
    ComboBox_Port.Items.Add(READER.GetString("2_IP"))
    ComboBox_Port.Items.Add(READER.GetString("3_IP"))
    ComboBox_Port.Items.Add(READER.GetString("4_IP"))
End While

Upvotes: 0

mark_h
mark_h

Reputation: 5477

if you add new items without first removing the old ones then this would be expected behaviour. To remove all items from your combobox before you add your new set you would need to clear its objectCollection like this;

ComboBoxA.ObjectCollection.Clear()
'now add your new set of items...

Upvotes: 0

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