c# where clause, instead of for loop-CodePudding

In my C# Form script, I have array which contains like 2-3k elements. I need to find a specific value in that array but without applying for loop to it. Looping trough 2-3k elements will cause couple of seconds delay, and i dont want that. This is similar to Mysql database for a website.

In PHP websites i was using where clause on indexed database, so even if the table had 1 milion rows, i was able to get the only row i needed in 0.020 second. Is there something similar for C#?

Here is what i'm trying to achieve.

using System;
using System.Linq;
                    
public class Program
{
    public static float[] data = {140, 160, 170, 180, 190, 54235243,234,4213,1234,543,1234,3215,52134,1234,222,333,444,555,666,777,888,999};
    
    public static void Main()
    {
        var queryLowNums =
            from num in data
            where num > 140 and num < 170
            select num;
        
        // num should be 160
        
    }
}

This code above is invalid ofc, im just trying to give example of what im trying to do. Is there such syntax/command or whatever, anything that can help me in this situation. Looping trough 2-3k elements will take like a second maybe or 2 seconds idk. I know that if i have the index of a given element, it will load it directly without the need of for loop. But idk how to achieve that.

CodePudding user response：

Use List

var list = new List<float>() { 140, 160, 170, 180, 190 };
var index = list.IndexOf(160);

 var values = list.Where(x=>x > 140 && x < 190); //it`s work very fast

CodePudding user response：

try this

 
    float[] data = { 140, 160, 170, 180, 190, 54235243, 234, 4213, 1234, 543, 1234, 3215, 52134, 1234, 222, 333, 444, 555, 666, 777, 888, 999 };

    float queryLowNums = 0;
    var startIndex = 0;
    Parallel.For(startIndex, data.Length, (j, state) =>
   {
       if (data[j] > 140 && data[j] < 170)
       {
           queryLowNums = data[j];
           state.Break();
       }
   });

output

or if you are expecting several numbers

    var primeNumbers = new ConcurrentBag<float>();

    Parallel.ForEach(data, number =>
    {
       if (number > 140 && number < 170)
        {
            primeNumbers.Add(number);
        }
    });

using a hash table would be much faster, but in your case if you don't have it , it takes less time to find an item then to create a hash table if it is not exist. The same about sorting algorithms.