C#小數點格式化

1.ToString()方法 

double d=12345678.2334; 
Console.WriteLine(d.ToString("F2")); //1234.23 
Console.WriteLine(d.ToString("###,###.00")); //12,345,678.23

2.Math.Round()方法 

Math.Round(3.44, 1); //Returns 3.4. 
Math.Round(3.45, 1); //Returns 3.4. 
Math.Round(3.46, 1); //Returns 3.5. 
Math.Round(3.445, 1); //Returns 3.4. 
Math.Round(3.455, 1); //Returns 3.5. 
Math.Round(3.465, 1); //Returns 3.5. 
Math.Round(3.450, 1); //Returns 3.4.(補0是無效的) 
Math.Round(3.4452, 2); //Returns 3.45. 
Math.Round(3.4552, 2); //Returns 3.46. 
Math.Round(3.4652, 2); //Returns 3.47. 

"四舍六入五考慮，五后非零就進一，五后皆零看奇偶，五前為偶應舍 去，五前為奇要進一" 
短一點的口訣叫“四舍、六入、五湊偶”

3.double.Parse()方法 

double   d=1.12345;   
d=double.Parse(d.ToString("0.00"));  //1.12

4.String.Format()方法

string str1 = String.Format("{0:N1}",56789); //result: 56,789.0 
string str2 = String.Format("{0:N2}",56789); //result: 56,789.00 
string str3 = String.Format("{0:N3}",56789); //result: 56,789.000 
string str8 = String.Format("{0:F1}",56789); //result: 56789.0 
string str9 = String.Format("{0:F2}",56789); //result: 56789.00 
string str11 =(56789 / 100.0).ToString("#.##"); //result: 567.89 
string str12 =(56789 / 100).ToString("#.##"); //result: 567

原文鏈接：http://qubernet.blog.163.com/blog/static/17794728420121102123822/