Example 3_9 Nesting of loop statements

Topic description 

Create a C# Windows application, enter the number of triangle rows, and print the effect as shown.

1> First add 2 Label controls, 1 TextBox, and 1 Button control to Windows Forms. The main property settings of each control are listed in the following table.

controls	Attributes	property settings	controls	Attributes	property settings
label1	Text	Triangle rows:	textBox1	Name	txtNum
label2	Text	""	button1	Name	btnOk
	Name	lbShow		Text	Print

2> Double-click the "btnOk" button in the form design area, the system automatically adds the "Click" event and the corresponding event method for the button, and then edit the code in the source code view .

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Test3_9
{
    public partial class Test3_9 : Form
    {
        public Test3_9()
        {
            InitializeComponent();
        }

        private void btnOK_Click(object sender, EventArgs e)
        {
            int n = Convert.ToInt32(txtNum.Text);
            StringBuilder sb = new StringBuilder();
            int i, j;
            for (i = 0; i <= n; i++)
            {
                for (j = 1; j <= n - i; j++)
                {
                    sb.Append(" ");
                }
                for (j = 1; j <= 2 * i - 1; j++)
                {
                    sb.Append("*");
                }
                sb.Append("\n");
            }
            lblShow.Text = sb.ToString();
        }
    }
}