Why does the combobox using the keyboard up & down arrows not reflect the textbox in vb.net

Question

Why does the combobox using the keyboard up & down arrows not reflect the textbox in vb.net.

So I want the up and down arrows on the keyboard to still appear in the textbox

I use the String.Equals Method to check the value selected in the combox is correct or not by referring to the textbox.

Please Guide Me

Thanks

Public Class Form4
 Public Sub New()
        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        ComboBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend
        ComboBox1.AutoCompleteSource = AutoCompleteSource.CustomSource
    End Sub
    Private Sub Form4_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ComboBox1.AutoCompleteCustomSource = AutoSuggestList()
    End Sub
    Private Function AutoSuggestList() As AutoCompleteStringCollection
        Dim collection As New AutoCompleteStringCollection
        Using connection As New OleDbConnection(GetOledbConnectionString())
            collection.AddRange(connection.Query(Of String)("SELECT ColorCode FROM ColorCode").ToArray)
        End Using
        Return collection
    End Function
    Private Sub GetItemData(ByVal iditem As String)
        Dim item = COLORCODESERVICE.GetByColorcode2(iditem)
        If item IsNot Nothing Then
            If String.Equals(iditem, item.Colorcode, StringComparison.CurrentCultureIgnoreCase) Then
                ComboBox1.Text = item.Colorcode
            End If
            TextBox1.Text = item.Colorname
            ComboBox1.Text = item.Colorcode
        Else
            MsgBox("Not Found Colorcode...")
            ComboBox1.ResetText()
            TextBox1.Clear()
            Return
        End If
    End Sub
    Private Sub ComboBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles ComboBox1.KeyDown
        If e.KeyCode = Keys.Enter OrElse e.KeyCode = Keys.Up OrElse e.KeyCode = Keys.Down Then
            ComboBox1.Items.Add(ComboBox1.Text)
            GetItemData(ComboBox1.Text)
        ElseIf e.KeyCode = Keys.Back OrElse e.KeyCode = Keys.Delete Then
            ComboBox1.ResetText()
            TextBox1.Clear()
        End If
    End Sub
    Private Sub ComboBox1_TextUpdate(sender As Object, e As EventArgs) Handles ComboBox1.TextUpdate
        TextBox1.Clear()
    End Sub
End Class