create a regex object in C# with text bux input "\q"

Question

I am trying validate a string based on input(textbox.text) regex pattern.

Regex regX = new Regex(TextBox1.Text);

It is failing. But

Regex regX = new Regex(@"\q");

is working fine.

Can you suggest the best way to validate a string based on user regex pattern?

TextBox1.Text probably doesn't have a valid regex. Use the debugger to inspect the value in TextBox1.Text — Philippe Leybaert, Apr 25 '16 at 17:10
@Adi how is it failing? What's the error? Or does it just not work as expected? — Tibrogargan, Apr 25 '16 at 17:12
What is the user supposed to enter, a regex pattern or a literal? If it is a literal, just use `==` or `String.Contains()` — Wiktor Stribiżew, Apr 25 '16 at 19:31
I just wanted to get the input pattern at runtime and validate a string but seems that few regular expressions are not supported in C# (e.g *\q*). — Adi, Apr 26 '16 at 14:31

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

You could validate the pattern before using it like this:

public void DoSomething()
{
    string pattern = TextBox1.Text;

    if(IsRegexPatternValid(pattern))
    {
        Regex regX = new Regex(pattern);
    }
    else
    {
        // handle invalid patterns here
        return;
    }
}

public static bool IsRegexPatternValid(String pattern)
{
    try
    {
        new Regex(pattern);
        return true;
    }
    catch { }
    return false;
}

Source for validating: How to validate a Regular Expression?

Your code isnt showing up how you are using the button. But I guess you've bound the KeyDown or TextChanged handlers. In this case validating would be necessary.

This is a nice way to skip unsupported regex pattern for the particular language. — Adi, Apr 26 '16 at 14:33

create a regex object in C# with text bux input "\q"

1 Answers1