You would need to make sure that all of the words are in the dictionary, and then you would need to check for proper grammar, which is incredibly complex, given English grammar rules. Also, does the user need to enter an exact 'phrase' such as a password to validate it--or do they need to enter any non-garbage value? This page might help get you started Checking to see if something is "a phrase", as in, proper English, would be very difficult.
This is often done with IDs in patterns such as a (US) social security number (NNN-NN-NNNN).
If there is a pattern such as AAA-NN or AAANN, you could split the ID into 2 inputs one alpha, one numeric.
A label on the form can tell them to use ###AA or whatever, but it seems silly to test the pattern and report a pattern error when you can simply tell them when it is invalid.
You could collect whatever they type and do a simple query to see if the ID exists, which after all is far more important than the pattern.
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Doing so can cause your application or the operating system to stop responding.
I want to validate empty textbox but once start app, this blocked and it shows the following exception error.
This calculate fine if the fields are filled but if some field is empty appears the error. Invalid Cast Exception HResult=-2147467262 Message=Input string was not in a correct format.
A masked text box is one way, counting the numerals and counting the letters is another.
Thank you again If the ID must be 3 numerals and 2 characters than there is probably also a pattern to it (as with many license plates) and more important than the mere character type count.
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