Operator is ambiguous on operands of type ulong and long in C#

Dear Sir, 

I have an error `Error CS0034 Operator '>=' is ambiguous on operands of type 'ulong' and 'long'` and `Error CS0034 Operator '<' is ambiguous on operands of type 'ulong' and 'long'` 

Please Guide me 

Thanks 

private void OnTick(object sender, EventArgs e)
{
    this._timeout = Win32.GetIdleTime();
    if (this._allowIdleWaitTime)
    {
        //error below line code

        if ((ulong)this._timeout < (long)this._duration && this._hasFinished)
        {
            this.StartNewTimer(this._durationAfterIdle);
            this.tmrTimeout.Stop();
            return;
        }
        if (this._hasFinished)
        {
            this.EndTimeout(null);
        }
    }
}


public void EndTimeout(object state)
{
    try
    {
        if (!this._allowIdleWaitTime)
        {
            if (!this.IsMouseWithinSnackbar() && !this._hasBeenInvoked)
            {
                base.Invoke(new Action(() => this.Close()));
                if (SnackbarView._action != null)
                {
                    base.Invoke(new Action(() => SnackbarView._action.DynamicInvoke(new object[] { SnackbarView._result })));
                    this._hasBeenInvoked = true;
                }
            }
        }
        //error below line code

        else if (((ulong)this._timeout >= (long)this._duration || this.IsMouseWithinSnackbar()) && (!SnackbarView._isDirectClosure || this._hasBeenInvoked))
        {
            this._hasFinished = true;
            this._timeout = 0;
        }
        else
        {
            base.Invoke(new Action(() => this.Close()));
            if (SnackbarView._action != null)
            {
                base.Invoke(new Action(() => SnackbarView._action.DynamicInvoke(new object[] { SnackbarView._result })));
                this._hasBeenInvoked = true;
            }
        }
    }
    catch (Exception exception)
    {
    }
}