c# - c# ToString a decimal and force + sign AND number 小数点以下の桁数

Question

tostring形式で2つのことを行うにはどうすればよいですか:

1. Display number to x decimal places
2. Also force a + sign so that negative an positive numbers lineup in nice columns.

string fmt = "+N" + dp + ";-N" + dp;
Console.WrtieLine(Open.ToString(fmt))

動作しません？