如何加速foreach结果

Question

I am making a Windows Forms application, and I want to generate numbers from 0 to 99999. I use the following code to print these numbers:

  private void button1_Click(object sender, EventArgs e)
    {
        int[] arr = Enumerable.Range(0, 99999).ToArray();
        var sb = new StringBuilder();
        foreach (int a in arr)
        {
            sb.AppendLine(a.ToString("000000"));
           // textBox3.Text += a.ToString("000000")+Environment.NewLine;
            textBox3.Text = sb.ToString();

        }
    }

But it takes lots of time to print all the numbers.

Is there any way to speed this up?

Answer 1

You set the text of the TextBox in each and every iteration . So the textbox is redrawn 100000 times. Of course it's slow.

Move the setting of the text outside the loop:

foreach (int a in arr)
{
    sb.AppendLine(a.ToString("000000"));
}
textBox3.Text = sb.ToString();

So you only set the text when you finished composing the string and the textbox is redrawn only once.

Answer 2

May be this help

 private void button1_Click(object sender, EventArgs e)
    {
        int[] arr = Enumerable.Range(0, 99999).ToArray();
        var sb = new StringBuilder();
        foreach (int a in arr)
        {
            sb.AppendLine(a.ToString("000000"));
           // textBox3.Text += a.ToString("000000")+Environment.NewLine;

        }
         textBox3.Text = sb.ToString();
    }

Answer 3

How about this approach.

    private void button1_Click(object sender, EventArgs e)
    {
        textBox3.Text = string.Join(Environment.NewLine, Enumerable.Range(0,99999).Select(x => x.ToString().PadLeft(6, '0')));
    } 

Answer 4

Have you tried this?

foreach (int a in arr)
{
    sb.AppendLine(a.ToString("000000"));
}
textBox3.Text = sb.ToString();