Value of type '1-dimensional array of Object' cannot be converted to 'System.Collections.ArrayList'.

Private Sub btn_login_submit_Click(sender As Object, e As EventArgs) Handles btn_login_submit.Click
        Dim loginService As LoginServiceReference.ILoginService
        Dim dt As New ArrayList
        dt = loginService.validateUser(txt_uname.Text, txt_psw.Text)

    End Sub
End Class

<ServiceContract()>
Public Interface ILoginService

    <OperationContract()>
    Function validateUser(uname As String, psw As String) As ArrayList

End Interface

Function validateUser(ByVal uname As String, ByVal psw As String) As ArrayList Implements ILoginService.validateUser
       Dim userStatus As Boolean = False
       Dim dc As New UserLoginDataContext()
       Dim udata As ArrayList = From t In dc.User_LoginInfos Where t.UserName = uname & t.U_password = psw Select t

       If (udata.Count > 0) Then
           userStatus = True
       Else
           userStatus = False
       End If

       udata.Add(userStatus)
       Return udata
   End Function