double noo = Convert.ToDouble(txttotalamount.Text);
noo = Math.Round(noo, 1);
                  
string numString = string.Format("{0:###0.00}", Math.Round(noo, 2, MidpointRounding.AwayFromZero));

try:

try:

roundnoo = Math.Round(noo, 2); 

或

or

转换十进制ToString(#.##")
这导致"12345.67"
从字符串中读取最后一个字符，并确定它应该向下还是向上(60或70)

Convert the decimal ToString("#.##")
this leads to "12345.67"
Read the last char from string and decide if it should be down or up (60 or 70)