CODEWITHSUNDEEP
c#
coop
coop

Reputation: 1

If a certain line in my text file is equal to a user inputted text box then

I've been doing a school project and I have a very poor understanding of C#

If a user inputs a certain name in a textbox and presses a button, it will compare each line of a text file to see if that name already exists in the text file named "NameList".

This is what I have so far and it doesn't seem to be working

        string substring = txtSearch.Text;
        string[] list = System.IO.File.ReadAllLines("NameList.txt");

        foreach (string s in list)
        {
            if (substring == s) 
            {
                lblUnsafe.Visible = true;
                lblSafe.Visible = false;

            }
            else
            {
                lblUnsafe.Visible = false;
                lblSafe.Visible = true;
            }
        }

When i input a name that is already in the text file, lblSafe becomes visible, which shouldn't happen.

I'm quite bad at explaining, i apologise, im happy to elaborate further if needed, thanks!

Upvotes: 0

Views: 103

Answers (2)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186668

You can

  1. Assume that the substring is not found
  2. Loop over file's lines
  3. Change visibility and break the loop on first finding

Code:

    string substring = txtSearch.Text;
    string[] list = ...
  
    // substring is not found yet 
    lblUnsafe.Visible = false;
    lblSafe.Visible = true;

    foreach (string s in list)
    {
        if (substring == s) 
        {
            // substring has been found: we change visibility... 
            lblUnsafe.Visible = true;
            lblSafe.Visible = false;

            // and break the loop: we've found what we wanted   
            break;
        }
    }

Usually for such problems we query the file with a help of Linq:

   using System.IO;
   using System.Linq;

   ...  

   // Do we have any line in the file such that...
   lblUnsafe.Visible = File
     .ReadLines("NameList.txt").Any(line => line == txtSearch.Text);

   // Safe is just Not Unsafe
   lblSafe.Visible = !lblUnsafe.Visible;

Upvotes: 1

Jcl
Jcl

Reputation: 28272

Your code is partially correct and you might be on the right way here... however in your code, you loop through all names in "NameList.txt", and set the visibility of lblSafe and lblUnsafe depending on if the current line you are looping on matches the textbox.

However once you match it, you continue looping... so let's find what happens:

User inputs: John, and your file contains Bob, John, Tom.

Your code does:

  • 1st loop: Bob == John? No, then set lblSafe to visible and lblUnsafe to invisible
  • 2st loop: John == John? Yes, then set lblSafe to invisible and lblUnsafe to visible
  • 3rd loop: Tom == John? No, then set lblSafe to visible and lblUnsafe to invisible

So the end state is that lblSafe becomes visible.

What you want to do instead is:

  • Set lblSafe to visible and lblUnsafe to invisible before looping
  • Then loop through all names
    • If the current loop name matches the textbox text, set lblSafe to invisible and lblUnsafe to visible and stop looping because we don't care about the rest

I'll leave the code to you, but it should be pretty easy, and except for a break statement to add, it's just reorganizing your own code

Upvotes: 1

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