using System;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        int height = 78;

        int width = 123;

        Obj[,] ObjArray = new Obj[width, height];

        string search_value = "112 : 54";

        for (int j = 0; j < height; j++)

        {

            for (int i = 0; i < width; i++)

            {

                ObjArray[i, j] = new Obj()

                {

                    property = String.Format("{0} : {1}", i, j)

                };

            }

        }

​

        Obj O = ObjArray.Cast<Obj>().FirstOrDefault(obj => obj != null && obj.property == search_value);

        Console.WriteLine(O == null ? "null" : O.property);

    }

​

    public class Obj

    {

        public string property { get; set; }

    }

}