利用asp.net实现生成不重复订单号

#region 生成单据号
/// <summary>
/// 生成单据号
/// </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