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Question

I have a class which has an ID and a few columns, one of which is a string.

public class myData
    {
        public Int64 myID { get; set; }
        public string myTitle{ get; set; }
        public string myForename{ get; set; }
        public string mySurname{ get; set; }
    }

There are a few million rows in the list and I want to search for all rows that have a mySurname that contains a specific string

I started to look at Contains but a little stuck on syntax where searching within a class, all examples I can find are only searching in a simple list of type string.

Ideally I want to get the full rows that match, or if not then the ID will do fine

Answer 1

Consider you have the following list:

List<myData> dta = new List<myData>()
{
    new myData()
    {
        myID = 1,
        mySurname = "tst"
    },
    new myData()
    {
        myID = 1,
        mySurname = "11test2"
    }
};

If you need to return in a list all the records that contain the word 'test' in the mySurname field, you can do it with 2 ways that are exactly the same:

1)

var res = dta.Where(d => d.mySurname.Contains("test")).ToList();

var res2 = (from d in dta
            where d.mySurname.Contains("test")
            select d).ToList();

Answer 2

You can use the LINQ

List<myData> list = new List<myData>();
myData m = list.Find(s=>s.mySurname==specificString);

Answer 3

Since you mentioned the arraylist tag, you can write a query like:

var data = new ArrayList();

data.Add(new myData { mySurname = "john 1" });
data.Add(new myData { mySurname = "john 2" });
data.Add(new myData { mySurname = "peter 1" });
data.Add(new myData { mySurname = "peter 2" });

var result = from myData item in data
             where item.mySurname.Contains("peter")
             select item;

foreach ( var item in result )
  Console.WriteLine(item.mySurname);

To have a List<myData> typed collection, you can also write:

var list = result.ToList()

Or if you need an ArrayList:

var dataFiltered = new ArrayList(result.ToArray());

foreach ( myData item in dataFiltered )

If you need to do a case insensitive search:

Case insensitive 'Contains(string)'

You should use a List<myData> instead of an ArrayList :

c# When should I use List and when should I use arraylist?

https://docs.microsoft.com/dotnet/api/system.collections.arraylist

Output

peter 1
peter 2