How would you implement filtering on multiple fields in Entity Framework?

Question

.NET

There is a filter like this:

return DbSet.Where(u => u.FirstName.IndexOf(search) > -1
                                    || u.LastName.IndexOf(search) > -1
                                    || u.UserName.IndexOf(search) > -1
                                    || u.Email.IndexOf(search) > -1);

Using the entered search word, the data is filtered.
Now I want to remake the algorithm in such a way that you can enter two words (Email LastName) and the data is already filtered based on two parameters. And the more parameters, the more accurate the filtering, i.e. as a result, one record that satisfies the condition may remain in the final table.
The idea was to do this:

return DbSet.Where(u => u.FirstName.IndexOf("WORDS ARRAY")) > -1
                                        || u.LastName.IndexOf("WORDS ARRAY") > -1
                                        || u.UserName.IndexOf("WORDS ARRAY") > -1
                                        || u.Email.IndexOf("WORDS ARRAY") > -1);

those. instead of WORD ARRAY, an array of words is passed and each parameter must choose the word that suits it for filtering, but it still doesn’t work out.

Answer 1

For array search - Array.IndexOf . I won’t say for sure if it will work in LINQ , I wouldn’t do it myself with data from the database. SQL is our everything :)

string[] arr = {"слово 1", "слово 2"};
return DbSet.Where(u => Array.IndexOf(arr, u.FirstName) != -1);

Another option, worse, but with the ability to ignore case:

string[] arr = {"слово 1", "слово 2"};
return DbSet.Where(u => arr.Any(itm=> itm == u.FirstName));