How check the 16 number for mastercard or Visa

Question

I have a dropdwonlast that ask use to choose mastercard or visa want they click or mastercard the textbox will check for mastercard want they click or visa the text box will check for visa

Vulpes · Answer

I'd use a RegularExpressionValidator for this: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.regularexpressionvalidator(v=vs.100).aspx The regular expressions needed to validate Visa or MasterCard are shown in this link: http://www.regular-expressions.info/creditcard.html