มันขึ้นว่าParameter @Country has no default value.

Imports System.Data
Imports System.Data.OleDb
Public Class dtcostom
    Private Sub dtcostom_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim conStr As String = "Provider=Microsoft.Ace.Oledb.12.0;Data Source=C:\Car\db\car.accdb;"
        Dim conn As New OleDbConnection(conStr)
        conn.Open()
        Dim ID_Car As String = Search.TbxID_Car.Text
        Dim SelecCountry As String = Search.CbCountry.SelectedItem
        Dim sql As String = "SELECT * FROM costommer WHERE ID_Car= @TbSearch and Country = @Country"
        Dim cmd As New OleDbCommand(sql, conn)
        cmd.Parameters.AddWithValue("TbSearch", ID_Car)
        cmd.Parameters.AddWithValue("Country", SelecCountry)
        Dim adapter As New OleDbDataAdapter(cmd)
        Dim data As New DataSet()
        adapter.Fill(data, "X")
        DataGridView1.DataSource = data.Tables("X")

    End Sub

    
End Class