Checking if string contains other strings

Question

This is simply an extension method which checks if a string str contains all the values in values.

However, there are cases when str might be null, values might be null, or any item in values might be null. I am handling those cases by using the ternary ?:, null-conditional ?. and null-coalesce ?? operators.

Should this piece of code be refactored?

public static bool ContainsAll(this string str, string[] values)
{
    return str == null ? false : values?.All(v => str.Contains(v ?? "")) ?? false;
}

I cannot pass null to string.Contains(), hence v ?? "" returns v, if non-null, otherwise "". — NotADeveloper
– NotADeveloper, Commented Jan 29, 2017 at 20:46
Now it looks much better and I give you +1 for the improvements ;-) — t3chb0t
– t3chb0t, Commented Jan 29, 2017 at 20:54

t3chb0t · Accepted Answer · 2017-01-29 21:26:11Z

8

I like the ternary operator but in this case I wouldn't use it because a single expression that makes sure both variables are valid and then searching for the strings is easier to understand I think.

The v ?? "" isn't very pretty, especially the "" part which actually should be string.Empty. You could get rid of it by filtering the array and skipping the empty and null elements.

public static bool ContainsAll(this string str, params string[] values)
{
    return 
        !string.IsNullOrEmpty(str) && 
        values != null &&
        values
            .Where(x => !string.IsNullOrEmpty(x))
            .All(v => str.Contains(v));
}

If you decorate the second parameter with params keyword then you can just type the values without an array (if you need to):

"text".ContainsAll("t", null);

edited Jan 29, 2017 at 21:26

answered Jan 29, 2017 at 21:03

t3chb0t

44.7k9 gold badges84 silver badges191 bronze badges

\$\begingroup\$ Personally I wouldn't go with string.Empty. But I'll leave it to whatever the preferences are for any one team. \$\endgroup\$

Measurity
– Measurity

2017-01-30 13:17:12 +00:00
Commented Jan 30, 2017 at 13:17

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