String.Format
//一般用法
//小數換算
string str3 = String.Format("{0:F2}", 0.125); //result: 0.13
string str4 = String.Format("{0:F3}", 0.125); //result: 0.125
string str5 = String.Format("{0:N1}", 123456.7891); //result: 123,456.8 四捨五入,N後面的數字表示保留幾個小數位數
string str6 = String.Format("{0:N2}", 123456.7891); //result: 123,456.79
string str7 = String.Format("{0:N3}", 123456.7891); //result: 123,456.789
decimal d = decimal.Round(decimal.Parse("0.55555"), 2); //result: 0.56 四捨五入
double d = Math.Round(0.55555, 2); //result: 0.56 四捨五入
double d = 0.55555;
string str8 = d.ToString("f2");//fN 保留N位，四捨五入
//小數點後面幾個0就保留幾個小數位數
string str9 = d.ToString("#0.00");
string str10 = (56789 / 100.0).ToString("#.##"); //result: 567.89
string str11 = (56789 / 100).ToString("#.##"); //result: 567
double num1 = 123456.123456;
string str = num1.ToString("#0.####");//幾個#等於顯示幾個小數位數且四捨五入
//output: 123456.1235
