C＃如何使标签的第一个字母可见

Question

I have created a Windows Forms application and I am using label_1.Visible = false; to make my label invisible.

I want to only make the first letter of the label visible.

How can I do it?

Answer 1

Visibility is all-or-nothing concept: if a label, or any other component for that matter, is marked invisible, none of it is going to appear on the form.

If you want to show only the first few letters of a string in a label, use Substring method to assign label's text. In order for this to work, the actual text must be stored somewhere outside the label - say, in labelText field:

private string labelText = "Quick brown fox";
...
label_1.Text = labelText.Substring(0, 1); // Only the first character is shown

Answer 2

Based on your answer to a comment, it sounded like you were interested in a Marquee-style display. Here's one way to do that, by storing the whole string in one variable, and then only displaying parts of it in a label.

In the example below, we have a string of text to display stored in a variable. We add a label to display the text, and a timer is used to repeatedly change the text to make it appear that it's scrolling.

To see it in action, start a new Windows Forms Application project and replace the partial form class with the following code:

public partial class Form1 : Form
{
    // Some text to display in a scrolling label
    private const string MarqueeText = 
        "Hello, this is a long string of text that I will show only a few characters at a time. ";

    private const int NumCharsToDisplay = 10; // The number of characters to display
    private int marqueeStart;                 // The start position of our text
    private Label lblMarquee;                 // The label that will show the text

    private void Form1_Load(object sender, EventArgs e)
    {
        // Add a label for displaying the marquee
        lblMarquee = new Label
        {
            Width = 12 * NumCharsToDisplay,
            Font = new Font(FontFamily.GenericMonospace, 12),
            Location = new Point {X = 0, Y = 0},
            Visible = true
        };
        Controls.Add(lblMarquee);

        // Add a timer to control our marquee and start it
        var timer = new System.Windows.Forms.Timer {Interval = 100};
        timer.Tick += Timer_Tick;
        timer.Start();            
    }

    private void Timer_Tick(object sender, EventArgs e)
    {
        // Figure out the length of text to display. 
        // If we're near the end of the string, then we display the last few characters
        // And the balance of characters are taken from the beginning of the string.
        var startLength = Math.Min(NumCharsToDisplay, MarqueeText.Length - marqueeStart);
        var endLength = NumCharsToDisplay - startLength;

        lblMarquee.Text = MarqueeText.Substring(marqueeStart, startLength);
        if (endLength > 0) lblMarquee.Text += MarqueeText.Substring(0, endLength);

        // Increment our start position
        marqueeStart++;

        // If we're at the end of the string, start back at the beginning
        if (marqueeStart > MarqueeText.Length) marqueeStart = 0;            
    }

    public Form1()
    {
        InitializeComponent();
    }
}

Answer 3

Strings are technically byte arrays, meaning each letter can be accessed with an index.

For example:

string x = "cat";
char y = x[0];
// y now has a value of 'c'!

Perform this on the string being used for your label and use the result for your label instead. I want to also add that you need to set label_1.Visible = true; otherwise nothing will appear at all.

Applying the above to your code, you should arrive at something like this:

label_1.Visible = true;
label_1.text = label_1.text[0].ToString();

Hope that works for you!