TextBox filter using Regex

Question

I am struggling to apply a filter on a TexBox. I have 3 filter types:

1) Only Numbers (positive) Example: 123 good, -123, ad8, 12.0 not good

2) Only Numbers plus "^" and "." chars Example: 123^3, -34, -34.5 good, ad8, 23-4 not good

3) Only POSITIVE Numbers plus "^" and "." chars Example: 123^3, 34.5 good, -34, ad8, 23-4 not good

Here is my work:

private void PriceInput_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox tb = sender as TextBox;

            switch (FieldType)
            {
                case InputFieldType.TypeQuantity:
                    tb.Text = KeyFilter.ExtractNumbersOnly(tb.Text);
                    break;
                case InputFieldType.TypePositivePrice:
                    tb.Text = KeyFilter.ExtractPositivePricesOnly(tb.Text);
                    break;
                case InputFieldType.TypePrice:
                    tb.Text = KeyFilter.ExtractPricesOnly(tb.Text);
                    break;
            }
        }

and KeyFilter:

public static string ExtractNumbersOnly(string s)
{
    Match match = System.Text.RegularExpressions.Regex.Match(s, "\\d+");

    return match.Value;
}

public static string ExtractPricesOnly(string s)
{
    Match match = System.Text.RegularExpressions.Regex.Match(s, "^[-]?\\d+([.]\\d+)?$");

    return match.Value;
}

public static string ExtractPositivePricesOnly(string s)
{
    Match match = System.Text.RegularExpressions.Regex.Match(s, "^[+]?\\d+([.]\\d+)?$");

    return match.Value;
}

You forgot to allow for the "^" character in 2/3. Should be: ^(?:[-]?\\d+(?:[.]\\d+)?)(?:\^[-]?\\d+(?:[.]\\d+)?)?$ and ^(?:\\d+(?:[.]\\d+)?)(?:\^[-]?\\d+(?:[.]\\d+)?)?$ respectively. This allows for things like -5.5^1.25 and 5.5^-1.25 respectively. — tenub
– tenub, Commented Mar 11, 2014 at 17:43

La-comadreja · Accepted Answer · 2014-03-11 18:41:05Z

1

(1)

^\\d+$

(2)

^-?\\d+(\\.\\d+)?(\\^)?(-?\\d+(\\.\\d+)?)?$

(3) actually easier than (2). Just take (2) and remove the negative signs.

^\\d+(\\.\\d+)?(\\^\\d+(\\.\\d+)?)?$

edited Mar 11, 2014 at 18:41

answered Mar 11, 2014 at 17:39

La-comadreja

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2 Comments

Alexandru Circus Over a year ago

I tried ^-?\\d+(\\.\\d+)?(\\^-?(\\.\\d+)?)?$ but now now does not let me to enter 123^4, only 123^ or 123

La-comadreja Over a year ago

@AlexandruCircus I have incorporated your suggestion for (2). Was designed to NOT take 123^

Sabuj Hassan · Accepted Answer · 2014-03-11 17:43:03Z

1

The required three regex are sequentially(as you asked) at below:

^\d+$

^-?\d+[.^]\d+$

^\d+[.^]\d+$

Please escape the \ with your escape character in C#

answered Mar 11, 2014 at 17:43

Sabuj Hassan

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3 Comments

Alexandru Circus Over a year ago

^-?\\d+[.^]\\d+$ does not find any match when I enter digit. eg:8

Sabuj Hassan Over a year ago

@AlexandruCircus It wasn't in your example. place a ? after [.^]. Which means [.^]?

Sabuj Hassan Over a year ago

@AlexandruCircus Sorry, it was. I missed it!

sallushan · Accepted Answer · 2014-03-11 18:53:08Z

1

Regex.IsMatch("123", "^\\d+$")
Regex.IsMatch("-123^33", "^-?\\d+((\\^\\d+)|(\\.\\d+))?$")
Regex.IsMatch("123^33", "^\\d+((\\^\\d+)|(\\.\\d+))?$")

Note that 2nd and 3rd does NOT work if ^ and . both are included, e.g. 123.44^2 <- as per given RegEx, this is NOT a correct input

answered Mar 11, 2014 at 18:53

sallushan

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