当ComboBox值更改时，如何更改TextBox的可见性？

Question

I'm new to programming and I'm trying to change the value of a textbox depending of a selected value on a combo box, since the values are numerical 1 to 20, and depending on the selection it will be the number of text boxes visible. I'm using the event selected index changed.

Here is my code:

private void cbxPIN_SelectedIndexChanged(object sender, EventArgs e)
{
    int pines = Convert.ToInt32(cbxPIN.SelectedItem.ToString());
    if (pines == 1)
    {
        textbox1.visible = true;
    }
    else if (pines == 2)
    {
        textbox1.visible = true;
        textbox2.visible = true;
    }
 ...

    else if (pines == n)
    {
        textbox1.visible = true;
        textbox2.visible = true;
 ...
        textboxn.visible = true;
    }
}

since there are like 25 different numeric values on the combo box is there an easier way of doing this? asides from comparing each different value?

Something like a loop.

Answer 1

At the least, I'd rewrite it like this, to reduce duplication:

private void cbxPIN_SelectedIndexChanged(object sender, EventArgs e)
{
    int pines = Convert.ToInt32(cbxPIN.SelectedItem.ToString());

    if (pines >= 1)
        textbox1.Visible = true;

    if (pines >= 2)
        textbox2.Visible = true;

    ...

    if (pines >= n)
        textboxn.Visible = true;
}

Actually, I'd add all the TextBox controls to a collection, possibly in the constructor:

List<TextBox> TextBoxes = new List<TextBox> { textbox1, textbox2, ... textboxn };

Then use LINQ's Take() method to grab the first xx number of controls and iterate through them:

foreach (var tb in TextBoxes.Take(pines))
    textBox.Show();

Answer 2

You want to use a loop structure. You should validate that the number of loops to perform is > 0 and < the number of textboxes you have available, but I'll leave error handling to you.

private void cbxPIN_SelectedIndexChanged(object sender, EventArgs e)
{
    int pines = Convert.ToInt32(cbxPIN.SelectedItem.ToString());
    TextBox textBox;
    for (int i = 1; i <= pines; i++)
    {
        // get the control from the form's controls collection by the control name
        textBox = this.Controls["textbox" + pines.ToString()] As TextBox
        textBox.Visible = true;
    }
}