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I have a list like this:

item.Add("a");
item.Add("as");
item.Add("b");
item.Add("fgs");
item.Add("adsd");

How can I find all items that start with (for example) "a"?

This "a" is not some hardcoded string, so I will need a function that do this for each string.

I try with FindAll, but I did not figured out how it works.

Br, Wolfy

Answer 1

If by "start with" you mean the first char, then:

item.FindAll(i => i[0] == 'a');

if you mean a string (may be other than 1 char) then:

item.FindAll(i => i.StartsWith("a"));

If you want a different comparison, such as case-insensitive, locale-based, etc. then do the relevant IndexOf such as:

item.FindAll(i => i.IndexOf("a", StringComparison.CurrentCultureIgnoreCase) == 0);

All of the above can be easily adapted to be use a relevant char or string variable or parameter.

If you don't need the extra properties and methods provided by a list, then it will be more efficient to use Where than FindAll as FindAll creates a new list, and does so in all at once, while Where will enumerate the matching results as it is iterated through.