Format a number with commas:
int i = 10000000; string s = i.ToString("N"); //10,000,000.00 string s2 = i.ToString("00,000,000"); //10,000,000 string s3 = i.ToString("#,0"); //10,000,000
double i = 10000000.3469; string s = i.ToString("#,0.000"); //10,000,000.347 string s2 = i.ToString("#,0.00"); //10,000,000.35
int i = 42; string s = i.ToString("D4"); //0042 string s2 = i.ToString("D5"); //00042 string s3 = i.ToString().PadLeft(5,'0'); //00042 string s4 = i.ToString().PadLeft(5,'%'); //%%%42
double i = 10000000.3469; string s = i.ToString("0.000"); //10000000.347 string s2 = i.ToString("#,0.000"); //10,000,000.347