C＃-嵌套循环

Question

I'm doing a simple c# exercise. The problem is I want to show output such as:

Output

Sample 1 => a

Sample 2 => b

Sample 1 => c

Sample 2 => d

Sample 1 => e

Sample 2 => f

Here's input 1 :

Sample 1 => 
Sample 2 => 

Here's input 2 :

a
b
c
d
e
f

Here's my code

foreach (string input1 in RichTextBox1.Lines)
{
    foreach (string input2 in RichTextBox2.Lines)
    {
        RichTextBox3.Text += input1 + input2 + Environment.NewLine;
    }
}

But it doe's not work .can anyone help me. thank you..

Answer 1

You need to corresponding elements of two sequences. So you can use LINQ's Zip method easily to achieve this result like this (Also by using String.Join method we didn't use any loop.):

richTextBox3.Text = String.Join(Environment.NewLine, 
                    Enumerable.Repeat(richTextBox1.Lines, richTextBox2.Lines.Count())
                    .SelectMany(c => c).Zip(richTextBox2.Lines, (f, s) => f + " => " + s));

Answer 2

You can try using modulo (%), and use RichTextBox2.Lines as the outer loop.

for (int i=0; i<RichTextBox2.Lines.Length; i++)
{
    var length = RichTextBox1.Lines.Length;
    RichTextBox3.Text += RichTextBox1.Lines[(i%length)] + RichTextBox2.Lines[i] + Environment.NewLine;
}

Looks complicated, but modulo gives you what you want even if there is a Sample 3, Sample 4, and so on.

Answer 3

Here is the code that would give you the expected output:

int i = 0;
foreach (var input2 in RichTextBox2.Lines)
{
    string input1 = RichTextBox1.Lines[i % RichTextBox1.Lines.Length];
    RichTextBox3.Text += input1 + input2 + Environment.NewLine;
    i++;
}

Answer 4

Your problem is that your are looping your second input ... for each first input! Again, and again, and again.

So: you only need one loop here. Here is some pseudo code to get started:

... first check that both line counts are equal
for (int i=0; i<linecount; i++) {
    RichTextBox3.Text += input1[i] + input2[i] + Environment.NewLine
}

Where input1[i] basically translates to: you have to push the content of your two initial boxes into an array for example.