It could be something like
const string numericFormat = "###,###,###,###,###,###,###";
decimal myValue =
myTextBox.Text = myValue.ToString(numericFormat);
For further detail, please see:
http://msdn.microsoft.com/en-us/library/system.decimal.aspx[
^],
http://msdn.microsoft.com/en-us/library/fzeeb5cd.aspx[
^],
http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx[
^],
http://msdn.microsoft.com/en-us/library/0c899ak8.aspx[
^].
[EDIT]
This format is already globalized. Even though the format notation of ',' is used, in formatted string it will appear as ',' or '.', depending on current thread culture.
I appreciate Matt for a fix and a useful note on globalization, please see the comments below.
—SA