C# 在購物車系統中生成不重復的訂單號[轉]

#region 生成單據號
/// <summary>
/// 生成單據號
/// </summary>
/// <param name="pFromType"></param>
/// <returns></returns>
public static string GetFormCode(FormType pFromType)
{
    string formcode = "";
    switch(pFromType)
    {
    case FormType.CaiGou:
    {
        formcode = "CG";
        break;
    }
    case FormType.ChaiXie:
    {
        formcode = "CX";
        break;
    }
    case FormType.ChuKu:
    {
        formcode = "CK";
        break;
    }
    case FormType.LingLiao:
    {
        formcode = "LL";
        break;
    }
    case FormType.PeiChang:
    {
        formcode = "PC";
        break;
    }
    case FormType.RuKu:
    {
        formcode = "RK";
        break;
    }
    case FormType.ShengChan:
    {
        formcode = "SC";
        break;
    }
    case FormType.SunYi:
    {
        formcode = "SY";
        break;
    }
    case FormType.TuiHuo:
    {
        formcode = "TH";
        break;
    }
    case FormType.XiaoShou:
    {
        formcode = "XS";
        break;
    }
    case FormType.PeiSong:
    {
        formcode = "PS";
        break;
    }
    case FormType.ZengPin:
    {
        formcode = "ZP";
        break;
    }
    case FormType.FuKuan:
    {
        formcode = "FK";
        break;
    }
    case FormType.ShouKuan:
    {
        formcode = "SK";
        break;
    }
    }
    formcode += DateTime.Now.Year.ToString();
    formcode += DateTime.Now.Month.ToString().Length == 1?"0" + DateTime.Now.Month.ToString() : DateTime.Now.Month.ToString();
    formcode += DateTime.Now.Day.ToString().Length == 1?"0" + DateTime.Now.Day.ToString() : DateTime.Now.Day.ToString();
    formcode += DateTime.Now.Hour.ToString().Length == 1?"0" + DateTime.Now.Hour.ToString() : DateTime.Now.Hour.ToString();
    formcode += DateTime.Now.Minute.ToString().Length == 1?"0" + DateTime.Now.Minute.ToString() : DateTime.Now.Minute.ToString();
    formcode += DateTime.Now.Second.ToString().Length == 1?"0" + DateTime.Now.Second.ToString() : DateTime.Now.Second.ToString();
    if(DateTime.Now.Millisecond.ToString().Length == 1)
    {
        formcode += "00" + DateTime.Now.Millisecond.ToString();
    }
    else if (DateTime.Now.Millisecond.ToString().Length == 2)
    {
        formcode += "0" + DateTime.Now.Millisecond.ToString();
    }
    else
    {
        formcode += DateTime.Now.Millisecond.ToString();
    }
    return formcode;
}
#endregion
//該代碼片段來自於: http://www.sharejs.com/codes/csharp/6004