C＃中的此switch语句有什么问题？

Question

I am trying to take a value from a user then every click on the button it must print statement and a picture that represent a number of trying. The if statement is working but it always shows the pic of last case.

private void button1_Click(object sender, EventArgs e)
{
    if (textBox1.Text != "")
    {    
        int gussednum= Convert.ToInt16( textBox1.Text); 

        for (int i = 0; i < 7; ++i)
        {
                if (interednum < num)
                {
                    label1.Text = "Should be greater than" + num;
                    switch (i)
                    {
                        case (0) :
                            Image image = Image.FromFile("1.png");
                            pictureBox1.Image = image;
                            break;

                        case (1):
                            Image im2 = Image.FromFile("2.png");
                            pictureBox1.Image = im2;
                            break;

                        case (2):
                            Image im3 = Image.FromFile("3.png");
                            pictureBox1.Image = im3;
                            break;

                        case (3):
                            Image image4 = Image.FromFile("4.png");
                            pictureBox1.Image = image4;
                            break;

                        case (4):
                            Image image5 = Image.FromFile("5.png");
                            pictureBox1.Image = image5;
                            break;

                        case (5):
                            Image image6 = Image.FromFile("dead.gif");
                            pictureBox1.Image = image6;
                            break;

                        case (6):
                            Image image7 = Image.FromFile("red.png");
                            pictureBox1.Image = image7;
                            break;
                    }
                }

Answer 1

You always assign an image to pictureBox1. And obviously the last time in the loop the last switch/case is executed (#7)

pictureBox1.Image = image5;

So, you either mistyped pictureBox1 on copy/pasting, or you should break a loop as well (from your switch/case break).

I am not sure if that's even StackOverflow question but just some copy/paste issue.

Answer 2

Since you've wrapped the switch/case with this for loop :

for (int i = 0; i < 7; ++i)

Whenever, the following is true :

interednum < num

You'll always have i equal to 6 because it loops to it every run. This is why it'll always output the last case .

This may or may not be an issue, but worth looking at. It seems you always change the same object ( pictureBox1 ):

pictureBox1.Image = image7;

You may have more than one pictureBox object, so it may look like this instead:

pictureBox7.Image = image7;//do this for every pictureBox in every case statement

Answer 3

It's run in loop so it's insert first image, next second and so on until the last. Possible it's to fast to see it and that's why u see only last image. Try to debug that program to see it's true.

My advice: just change all break's commands for "return" in switch case. That's all.

Ps. This code doesn't have sense in my opinion (i saying about switch case in for loop ;)).