How to have textbox regular expression validation on asp.net?

what is the difference between digits and units?
Please show a sample of valid and invalid entries

1.0 to 999.99 is valid

If user entered 500.000 , it will not allow user to enter more than 500.00  or round it up.

In other words .. user cant type 100.00000000 ..  decimal units should be stopped at 2 digit units.

I don't know ASP but the regex would be this:

^\d{1,3}\.\d{1,2}$

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That will require at least one digit before and after the decimal with a max of 3 before and 2 after.

This is my solution. It works.

But .. what it happens . is that, it allows the user to enter the number as 100.000000

and then prompt a message.

Instead of doing that, is there a way to prevent the user to type more than .00 digits.

Also i am using <Input> syntax. Instead of ValidationExpression, i am using the attribute : pattern

I'm guessing there isn't a way to do that but, as I said, I don't know ASP (just regexes).

Anyways, for now i am good. Thanks for helping me !!!!

@Wilcoxon

Regex which you shared : ^\d{1,3}\.\d{1,2}$


When we enter the digit as 100 , it doesn't take it. It is expecting to enter the digit as 100.00
decimal unit should be optional as well as decimal unit should not exceed more than 2 units.

This is my current syntax :

[RegularExpression(@"\d{1,3}\.\d{1,2}$", ErrorMessage = "Invalid.")]
[Range(60.00, 120.00, ErrorMessage = "Invalid.")]

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Is there some reason that you did not give me partial credit for providing the regex (the same one that David Johnson used in his code)?

Based on your original post and your first comment, it appeared you were saying that at least one decimal digit was required.  To make it optional, change the regex to:

^\d{1,3}(?:\.\d{1,2})?$

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Now it will accept anything from 0 to 999.99 (if 0 should not be allowed then change the first \d{1,3} to [1-9]\d{0,2}).