Failed 2 out of 5 test cases, how can I improve my code ?

Question

Explanation:
If you remove everything that isn't a letter or space from the original message and flip it around, you get "hello world"
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Textsing System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
string input = Console.ReadLine();
var output = new char[] {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','.','_'};
var result = string.Join("",(from x in input.ToCharArray() where output.Contains(x) select x.ToString()).ToArray());
char[] reverse = result.ToCharArray();
Array.Reverse(reverse);
string reversed = new string(reverse);
Console.WriteLine(reversed);
}
}
}

Answer 1

Exactly, you should keep space, not fullstop and underscore.

So your output array is containing the wrong elements, and so the output.Contains(x) is doing wrong screening.

See?

Answer 2

Go to the question page, read the text in yellow "Explanation" box, copy and paste it here.

Answer 3

Hi Bro,
Just modify space and try to
Avoid fullstop

Answer 4

You need to read the question carefully.

Currently your output array contains two non-valid elements and is missing one necessary elements.

Don't guess the rules by your assumptions, read the input-output example in specification and also the yellow Notes textbox.

Answer 5

So, what does the yellow text say?

What is its exact wordings?

Copy and paste its original wordings here.

Answer 6

No, you did it wrongly.

Apart from letters, what should be kept?

Answer 7

Thank you Gordon.

Answer 8

By practicing

Answer 9

Why do you mark your own answer as Best Answer?

Answer 10

Sorry, mistake.

Answer 11

Joseph Oritseweyinmi congratz on your dedication. Keep it like that and you're gonna go far.

Answer 12

Do practice daily, make note, Study new things daily and start challenge others

Answer 13

I don't understand.

Answer 14

Ok Gordon I'll do it.

Answer 15

Gordon I've done it.

Answer 16

I've already done it.

Answer 17

Space!.

Answer 18

Try to open another browsers and dowland wit link.

Answer 19

Add a space to the array and remove the '.' (dot) one

Answer 20

Its so easy