Is there a way to catch maximum length PER LINE and not allow user to input more characters if max length PER LINE has been reached?

Question

Good day!

Sorry if I cant make it into code but here\'s my problem:

Im coding C#, using TextBox Control, Multiline = true.

Now, my problem is i need

Answer 1

textBox.OnTextChanged += (EventArgs e) => // invoked on every text change
{
    var lines = myTextBox.Where(x.Length > 5); // Get the long lines
    for (var i; i < lines.Count(); i++)  // iterate over long lines
    {
        lines[i] = lines[i].Substring(0, 5); // replace the line with its substring(stripped) value
    }
}

Answer 2

You can extract them from the lines of the Textbox like:

var myarr = myTextBox.Lines.Select(n => n.Remove(3)).ToArray();

Btw, you're most likely better off with a DataGridView Control.

Answer 3

How about this, this should behave like the MaxLength property and handle the addition of the new char before it occurs, not after. When a key is pressed it checks the length of the line the cursor is currently on.

public class MaxPerLineTextBox : TextBox
{
    public MaxPerLineTextBox()
    {
        base.Multiline = true;
    }

    public override bool Multiline
    {
        get
        {
            return true;
        }

        set
        {
            throw new InvalidOperationException("Readonly subclass");
        }
    }

    public int? MaxPerLine { get; set; }

    protected override void OnKeyPress(KeyPressEventArgs e)
    {
        if (char.IsControl(e.KeyChar))
        {
            base.OnKeyPress(e);
            return;
        }

        int maxPerLine;
        if (this.MaxPerLine.HasValue)
        {
            maxPerLine = this.MaxPerLine.Value;
        }
        else
        {
            base.OnKeyPress(e);
            return;           
        }

        var count = 0;
        var lineLength = this.Lines.Select(line =>
            {
                count += line.Length;
                return new { line.Length, count };
            })
            .Last(c => c.count < this.SelectionStart).Length;

        if (lineLength < maxPerLine)
        {
            base.OnKeyPress(e);
            return;
        }

        e.Handled = true;
    }
}

Answer 4

You can handle OnTextChanged event and then use Lines property to get array of lines. Then simply check whenever any line has more characters than you allow and if so - correct it and set as a Lines again. You have to also prevent event from rising when you do such correction, use the flag or unsubscribe/subscribe technique.