I don´t know how to resolve a situation i have. I have a regular expression that validate a textbox input, what i need is to prevent or remove characters that not mach the regular expresion while the user is typing.
my regular expression is:
^[A-Z0-9]+(\.[A-Z0-9]+|[A-Z0-9]*)*$.
it allows letters,numbers, and dots (but no more than one consecutive), but it can be change without notificacion (by system configuration)
Any idea how to solve it?
Upd: it`s a winforms application
You could keep a local variable that stores the value of the textbox. On each keypress, check whether the key matches the regex. If so, add the character to the local variable, and set the textbox's text field to the variable. Otherwise set the textbox to the current value of the local variable, thus overwriting the bad input.
Use Custom validator with this regex.
Related
I have been developing an application that one of it's responsability is provide to user an page that it's possible to write math expression in EXCEL WAY.
It is an application in ASP.NET MVC, and it's use the SpreadSheetGear library to EXECUTE excel expression.
As it's show below, The page has an texarea to write expression and two button on the right. The green one is for VALIDATE THE EXPRESSION and the red one is for clean textarea.
A,B,C are parameter, that application will replace for values. Notice that it is not possible to know the parameter data type. I mean, if I write a concatenate function, It is necessary that user use double quotes (") to delimitate string. For example
CONCATENATE("A","B") thus, is necessary that user KNOW functions parameters and its correlate data types.
My main issue is how to validate the expression?
SpreadSheetGear there isn't any method to perform this validation.
The method spreadsheetgear provides to perform an formula is:
string formula = "{formula from textarea}"
worksheet.EvaluateValue(formula)
and it's expect and string.
As I don't know what formula user will write, or how many parameters this formula has and what are the parameters data type, it's kind difficult to validate.
Now my question is?
How could I validate the expression?
I think in an alternative: Provide to user and page with textbox for each parameter in the expression. The user will be able to provide some data and validate the RESULT of formula. If the sintaxe of formula is wrong the application throw an exception.
It would be a good solution, but for each "PROCESS" that user will interact to, He'll write 10, 15 formulas, and maybe it would be little painful.
Anyone could provide me an Good solution for that?
Thank you!
https://sites.google.com/site/akshatsharma80/home/data-structures/validate-an-arithmetic-expression
refer this site for validation
This is a very late response but I have been working on expression evaluators in Excel with VBA for a while and I might shed some light. I have three solutions to try but all have limitations.
1) Ask the user to put a '$' after a variable name to signify a string (or some other unique character). Drawback is that it is not as simple as typing a single letter for a variable.
2) Assume all variables entered are double precision. Then change the variable to strings in all combinations until one combination works. Could be very time consuming to try all the combinations if the user enters lots of individual variables.
3) Assume all variables entered are double precision. But then have a list in your program of functions that require strings for parameters. Then you could parse the expression, lookup the functions in your list and then designate the parameters that require string input with a string signifier (like in step 1). This will not account for user defined functions.
Now to test out the function, replace all the numeric variables with '1' and all the string variables with "a", then EvaluateValue. If you get a result or an error signifying a calculation error, it is good.
BTW, in order to parse the expression, I suggest the following method. I do not know C#, only VB, so I will only talk in general terms.
1) Take your expression string and do a search and replace of all the typical operators with the same operator but with a backslash ("\") in front and behind the operator (you can use any other character that is not normally used in Excel formulas if you like). This will delineate these operators so that you can easily ignore them and split up your expression into chunks. Typically only need to delineate +,-,/,*,^,<,>,= and {comma}. So search for a "+" and replace it with a "\+\" and so on. For parenthesis, replace "(" and ")" with "(\\" and "\\)" respectively.
So your sample formula "SUM(A, SQRT(B, C)) * PI()" will look like this:
"SUM(\\A\,\ SQRT(\\B\,\ C\\)\\) \*\ PI(\\\\)"
You can also clean up the string a bit more by eliminating any spaces and by eliminating redundant backslashes by replacing every three consecutive backslashes with a single one (replace "\\" with "\").
2) In Visual Basic there is a command called 'Split' that can take a string like this and split it into a one dimensional array using a delimiter (in this case, the backslash). There must be an equivalent in C# or you can just make one. Your array will look like this: "SUM(", "", "A", ",", "SQRT(", "", "B", etc.
Now iterate through your array, starting at the first element and then skipping every other element. These elements will either be a number (a numeric test), a variable, a function (with have a "(" at the end of it), a parenthesis or blank.
Now you can do other checks as you need and replace the variables with actual values.
3) When you are done, rejoin the array back into a string, without any delimiters, and try the Evaluate function.
I'm working on a text entry application that uses regular expressions to validate user input. The goal is to allow keypresses that fit a certain RegEx while rejecting invalid characters. One issue I've run into is that when a user starts inputting information they may create a string that doesn't yet match the given regex, but could cause a match in the future. These strings get erroneously rejected. Here's an example - given the following regex for inputting date information:
(0?[1-9]|10|11|12)/(0?[1-9]|[12]\\d|30|31)/\\d{2}\\d{2}
A user may begin entering "1/" which could be a valid date, but RegEx.IsMatch() will return false and my code ends up rejecting the string. Is there a way to "optimistically" test strings against a regular expression so that possible or partial matches are allowed?
Bonus: For this RegEx in particular there are some sequences which cause required characters. For example, if the user types "2/15" the only possible valid character they could enter next is "/". Is it possible to detect those scenarios so that the required characters could be automatically entered for the user to ease input?
What you can do is anchor your RegExp (i.e. adding ^ and $, as in start/end of line) and make some component optionnal for validation, but strictly defined if present.
Something looking like this:
^(0?[1-9]|10|11|12)(/((0?[1-9]|[12]\\d|30|31)(/(\\d{2}(\\d{2})?)?)?)?)?$
I do realize it looks horrible but as far as I know there is no way to tell the regexp engine to validate as long as the string satisfies the beginning of the regexp pattern.
In my opinion, the best way to achieve what you want to do is to create separate inputs for day/month/date and check their value when leaving the text field.
It also provides a better visibility and user-experience, as I believe no one likes to be prevented from typing certain characters into a text field with or without noticing them disappear as they type or having slashes inserted automatically and without notice.
Have you ever used and app or form that worked that way, simply refusing to accept any keypress it didn't like? If the answer is Yes, did it blow an electronic raspberry each time you pressed a wrong key?
If you really need to validate the input before the form is submitted, use a passive feedback mechanism like a red border around the textfield that disappears the regex matches the input. Also, make sure there's a Help button or a tooltip nearby to provide constructive feedback.
Of course, the best option would be to use a dedicated control like a date-entry widget. But whatever you do, don't do it in such a a way that it feels like you're playing guessing games with the user.
I've set MaskedTextBox's Mask to: "Fl\air H\al ###.## , something here: ####.##"
When user inputs the value final text looks something like this:
Flair Hal 987.67 , something here: 1234.12
What will be the best way to extract 976.67 and 1234.12 from the MaskedTextBox's Text. I am looking for a List which will have all the values of the mask (976.67, 1234.12).
There can be any number of masks in the mask string and the mask can be any valid mask.
I am thinking of first removing '\' from the Mask and then in a for loop keep comparing the Mask with the Text and detect changes and add them to the List. But this doesnt sound good to me and i think there probably is a better way of doing it.
There are four values of the mask in your example: 987, 67, 1234, 12. The fact that blocks separated by a . are treated as one is your own logic, so I think you will just have to write code to get the information yourself.
Have a look at the MaskedTextProvider property of the MaskedTextBox, and its EditPositions property. The EditPositions give you the positions within the Text that the user could enter.
Well i found out that there is no good way of doing it. As adrianbanks said i have to code myself to get this information.
I have written my own usercontrol which uses combination of labels and maskedtexboxes to get the input.
I use curly braces to indicate where i wan the masked textbox and the user control puts one masked textbox per pair of curly braces.
"Flair Hal {###.##} , something here: {####.##}"
Then I can use the values collection which has the values for the masks.
I would think that you would be to use TextMaskFormat to remove the literals and prompt characters from the .Text property. That way you'd only get the numbers (and spaces).
Use a regular expression. The following regex will work for your example, but you may have to tweak it depending on your actual mask:
\d*[.]\d{2}
I want to validate string containing only numbers. Easy validation? I added RegularExpressionValidator, with ValidationExpression="/d+".
Looks okay - but nothing validated when only space is entered! Even many spaces are validated okay. I don't need this to be mandatory.
I can trim on server, but cannot regular expression do everything!
This is by design and tends to throw many people off. The RegularExpressionValidator does not make a field mandatory and allows it to be blank and accepts whitespaces. The \d+ format is correct. Even using ^\d+$ will result in the same problem of allowing whitespace. The only way to force this to disallow whitespace is to also include a RequiredFieldValidator to operate on the same control.
This is per the RegularExpressionValidator documentation, which states:
Validation succeeds if the input
control is empty. If a value is
required for the associated input
control, use a RequiredFieldValidator
control in addition to the
RegularExpressionValidator control.
A regular expression check of the field in the code-behind would work as expected; this is only an issue with the RegularExpressionValidator. So you could conceivably use a CustomValidator instead and say args.IsValid = Regex.IsMatch(txtInput.Text, #"^\d+$") and if it contained whitespace then it would return false. But if that's the case why not just use the RequiredFieldValidator per the documentation and avoid writing custom code? Also a CustomValidator means a mandatory postback (unless you specify a client validation script with equivalent javascript regex).
Your question is a little hard to follow, but if you are asking how to write a regular expresion which only accepts digits I think your mistake is in using forward-slash instead of backslash. Try
"\d+"
The RegularExpressionValidator is a nice wrapper for doing regex checks but it will not validate against an empty control. You could use a CustomValidator and then do the regular expression check in a javascript function that you attach to the validator.
It will validate against an empty (blank) control as long as you set the ValidateEmptyText property to true.
You can read more about the CustomValidators on MSDN here.
try to use Ajax FilteredTextbox, this will not allow space.......
http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/FilteredTextBox/FilteredTextBox.aspx
Try using ^\d+$ to force the digits to fill the entire line.
^ = line start $ = line end
I have run into a problem trying to modify a form I myself have not built.
The form has a asp:input field for a date value, wich is checked by a requiredFieldVal and a rangeVal. The rangeVal has type set to "date" and min value 2000-01-01: max value 3000-01-01
Now to the problem, I'm trying to add so that the user also can input the date in the form of "20000101" in other words without the "-".
I tried adding another rangeVal with Integer type and the min,max values, and put them both in the same ValidationGroup, but that didnt work.
How do I allow the user to use both (either one of them) formats in the date input field.
Thank you in advance!
When you use multiple validation controls to validate a single control all of the validation controls must pass.
You could use a regular expression (as Kevin points out) but doing the validation you require (checking that the value is a valid DateTime object and within the specified range) will be difficult to do cleanly.
I'd suggest writing your own CustomValidator control and then use that to validate your values however you want to.
You can use a regular expression validator in place of the range validator. I'm a little rusty with Regex, but I am sure you can find something here.
http://www.regular-expressions.info/
Here is a link to the dates page:
http://www.regular-expressions.info/dates.html
try this, I think it will work. If not, let me know and I will work on correcting it:
((19|20)\d\d[- /.](0[1-9]|1[012])[-/.](0[1-9]|[12][0-9]|3[01])|((19|20)\d\d(0[1-9]|1[012])(0[1-9]|[12][0-9]|3[01])))
Another post brought up a point this regex won't validate some invalid dates like feb 31. In this case, I would just create a validation class which inherits from the regex validator and override the EvaluateIsValid method and check to see if it is an actual date. This allows most of the validation done on the client end, with the backup being at the server level which should be doing a secondary validation anyway.