Search method for array values inside a List (C#)

Question

I'm trying to create a search method in C# and I am stuck.

This is my method that I want to use to search for the array values inside my List object:

public void Search()
        {
            Console.Write("\tKeyword: ");
            string keyword = Console.ReadLine();

            List<string> searchResults = new List<string>();

            for (int a = 0; a < log.Count; a++)
            {
                foreach (string item in log[a])
                {
                    if (item.Contains(keyword))
                        searchResults.Add(item);
                }
            }

            Console.WriteLine("Search Results: ");
            for (int b = 0; b < searchResults.Count; b++)
            {
                Console.WriteLine("\t{0}\t{1}\t\t{2}", searchResults[b][0], searchResults[b][1], searchResults[b][2]);
            }

        }

This is my List that I want to search through:

private List<string[]> log = new List<string[]>();

This is how I add arrays into the List:

string[] arrOfLog = new string[4] {
            String.Format("{0:yyyy-MM-dd}", localDate),
            title,
            desc,
            null
        };

        log.Add(arrOfLog);

What can I do to search for title and description values?

I get the exception:

Object reference not set to an instance of an object.

`item.Contains()` will throw a `NullReferenceException` for `arrOfLog[3]`. — René Vogt, Feb 19 '17 at 15:22
I suggest to use a class for the entries instead of a string-array. — René Vogt, Feb 19 '17 at 15:23
Possible duplicate of [What is a NullReferenceException, and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Chris, Feb 19 '17 at 15:24
So what exactly is your question? Do you want to know what causes the exception and how to avoid it? Then it's a duplicate. Or do you only want to search for `title` and `desc`? — René Vogt, Feb 19 '17 at 15:25
I want to search for title and desc, sorry for a confusing question. — De2o, Feb 19 '17 at 15:27

Thili77 · Answer 1 · 2017-02-19T15:38:30.597

You can do this after creating a model class ,

public class model
{
    string localDate { get; set; }
    string title { get; set; }
    string desc { get; set; }
}

then using that you can search those separately.

This is the full code

public void Search()
{
    Console.Write("\tKeyword: ");
    string keyword = Console.ReadLine();

    List<string> moList = new List<string>();
    foreach ( var item in log )
    {
        model mo = new model();
        mo.localDate = log[0];
        mo.title = log[1];
        mo.desc = log[2];
    }

    List<string> searchResults = new List<string>();

    for (int a = 0; a < moList.Count; a++)
    {
        foreach (model item in moList[a])
        {
            if (item.title.Contains(keyword) || item.desc.Contains(keyword)){
                 searchResults.Add(item);
            }
        }
    }

    Console.WriteLine("Search Results: ");
    for (int b = 0; b < searchResults.Count; b++)
    {
         Console.WriteLine("\t{0}\t{1}\t\t{2}", searchResults[b][0], searchResults[b][1], searchResults[b][2]);
    }

}

score 0 · Answer 2 · answered Feb 19 '17 at 15:32

0

you could write item?.Contains(keyword) ?? false instead of item.Contains(keyword)
the ? does not call Contains if item is null, but you get null if item is null.
the ?? tells the compiler to use false if item is null.

answered Feb 19 '17 at 15:32

Matz Reckeweg

31
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Search method for array values inside a List (C#)

2 Answers2