How to block or restrict special characters from input fields?
Use regex to allow/disallow anything. Also, for a slightly more robust version than the accepted answer, allowing characters that don’t have a key value associated with them (backspace, tab, arrow keys, delete, etc.) can be done by first passing through the keypress event and check the key based on keycode instead of value.
Is there such a thing as special characters?
There’s no such thing as special characters. It all depends on the context that input is used within your application. Protecting against SQLi and XSS is great, however if the input is then to be used in an operating system shell call it does you no good.
When to use strange characters in input fields?
Again, if you have an input field for entering a name you probably don’t need strange characters such as “<>/\\;,!”. These characters are used when sending scripts into the input field and if they are blocked it will make it more difficult for an attacker.
Why are there no restrictions on input fields?
Lacking input restriction might be a sign of other security checks missing but can also be specifically used by hackers. An intruder might try to send in great amounts of data and hope that the system crashes and either grant administrator/root access or reveals unintended information.
Is it possible to inject code characters out of range?
Pay attention to trigger code characters (e.KeyChar lower then 32) if you use a RegExp. But in this way is still possible to inject characters out of range whenever the user paste text from the clipboard. Unfortunately I did not found correct clipboard events to fix this. So a waterproof solution is to intercept TextBox.TextChanged.
How to select all If parameter is empty or null?
SQL Query to Select All If Parameter is Empty or NULL. In general, when you create a SQL stored procedure or any query that accepts parameters, you might force the User to provide a value for that parameter. It is not the case in real-time, so you have to allow NULL values and empty strings.
Can someone help me create a regex to check if a string is empty?
Can someone help me create this regex. I need it to check to see if the string is either entirely whitespace (empty) or if it only contains positive whole numbers. If anything else it fails.