Try this expression first with your expression
System.Text.RegularExpressions.Regex.Replace(YourString,"(?<=\d)\,(?=\d+)").Tostring
The above will remove the comma, then you use this expression with the input string of above expressions output
System.Text.RegularExpressions.Regex.Replace(YourString,""|.00","").Tostring
Regards
Sudharsan