wpf textbox validation with regex

Question

I have a textbox in which I'm using the event TextChanged to check if the string is valid with RegEx and show a messagebox if it isnt. When testing the regex I have with online regex tool such as http://regexpal.com/ , it seems to be working fine. But when I run my code, it's not working as expected. I'm never seeing the messagebox show up. Any help would be appreciated. My regex is suppose to check any digits from 0-5 before the "." with two decimals if any.

private void txtValInput_TextChanged(object sender, TextChangedEventArgs e)
{
     string input = (sender as TextBox).Text; //1234567

     if(!Regex.IsMatch(input, @"^\d{1,5}|\d{0,5}\.\d{1,2}$"))
     {
           MessageBox.Show("Error!, check and try again");
     }
} 

Answer 1

您需要添加()以使正则表达式正确锚定，否则您的示例将匹配，因为正则表达式仅检查字符串开头是否有1到5位数字-以后可能会出现任何数字。

@"^(\d{1,5}|\d{0,5}\.\d{1,2})$"

Answer 2

The reason it isn't working is because you haven't encompassed your Regular Expression within () . Without that identifier it isn't able anchor your syntax correctly.

You would want your Expression to look like this:

@"^(\\d{1,5}|\\d{0,5}\\.\\d{1,2})$

Keep in mind you may have also added additional complexity to your Expression .

To elaborate:

• ^ : Will grab the first character or line.
• \\d : Will grab all the numeric characters.
• $ : Will stop at end of line or last character.

I'd like to take a second with that second one. If you actually do \\d+ it will grab all numeric characters and all that precede afterwards. Which may make your request slightly easier; but I'm unsure of what you are searching.

Hopefully that helps, I see a Grey 1 Answer Box so someone else posted so you should easily find a resolution Calvin.