Removing Lines from the textBox.

Question

I am Reading data from serialport. I just want 40 lines to appear in the textbox.

How I can erase lines older lines to make Place for new lines?

I tried the following code:

     int numOfLines = 40; 
    var lines = this.textBox1.Lines;
    var newLines = lines.Skip(numOfLines);
    this.textBox1.Lines = newLines.ToArray();

But it gives me error, saying that " 'string[]' does not contain a definition for 'Skip' and no extension method 'Skip' accepting a first argument of type 'string[]' could be found".

Answer 1

I think you have forgotten to add using System.Linq; directive

PS if you want last 40 lines to be appear, you can use approach described in this question: Using Linq to get the last N elements of a collection?

Answer 2

您需要添加对Linq的引用：

using System.Linq;

Answer 3

Skip is a extension method of LINQ. You must add a reference to System.Core in your project, and in case it's needed a using System.Linq; directive

Edit

As you seem to be "unable" to use LINQ, here is a non-LINQ solution (just as an experiment of reinventing the wheel):

Extension Methods

public static class ExtMeth
{
    public static IEnumerable<string> SkipLines(this string[] s, int number)
    {
        for (int i = number; i < s.Length; i++)
        {
            yield return s[i];
        }
    }

    public static string[] ToArray(this IEnumerable<string> source)
    {
        int count = 0;
        string[] items = null;
        foreach (string it in source)
        {
            count++;
        }
        int index = 0;
        foreach (string item in source)
        {
            if (items == null)
            {
                items = new string[count];
            }
            items[index] = item;
            index++;
        }
        if (count == 0) return new string[0];
        return items;
    }
}

Usage

this.textBox1.Lines = this.textBox1.Lines.SkipLines(2).ToArray();