Run only one instance from you program

private void XXXXX_Load(object sender, EventArgs e)
{
    string m_UniqueIdentifier;
    string assemblyName =
System.Reflection.Assembly.GetExecutingAssembly().GetName(false).CodeBase;
    m_UniqueIdentifier = assemblyName.Replace("\\", "_");
    m_Mutex = new Mutex(false, m_UniqueIdentifier);
    if (m_Mutex.WaitOne(1, true))
    {
    }
    else
    {
        //Not the first instance!!!
        m_Mutex.Close();
        m_Mutex = null;
        MessageBox.Show("Start only one Instance", "Allways runnning");
        this.Close();
    }