int i = 0;
bool ValueIsNumeric = int.TryParse(MyStringValue, out i);
For larger values
UInt64 i = 0;
bool ValueIsNumeric = UInt64.TryParse(MyStringValue, out i);
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.