添加新文本框时删除文本框的第一行

Question

I am using the following command to append text to a multiline textbox that I am using:

TextBox1.AppendText(Environment.NewLine & "Current status : " & currentStatus)

However, if there are (for example) 49 lines, I want to delete the first line when line 50 gets added.

How can I do this ?

Answer 1

You can also use LINQ to solve this problem. Here i have used SKIP and TAKE functions.

If textBox1.Lines.Count = 50 Then
    textBox1.Lines= textBox1.Lines.Skip(Of String)(1).Take(textBox1.Lines.Length - 1).ToArray()
End If

NOTE: It will only work if you have framework 3.5 or above.

Answer 2

Try this

dim sNewLine as String '-------> inserted text 
dim s as string = textbox1.text

s=mid(s,instr(s,vbCRLF)+2)

To append new line

textbox1.text = s & vbCRLF & sNewLine

Answer 3

The text box has a TextChanged event, which is fired every time the text changes.

You can use this to count the number of lines in the text box, which is the same as the number of newline characters. If this amount exceeds your limit, you can remove the first line by locating the first newline character and remove it and everything in front of it.

I don't speak VB.Net, so I hope you can work with this and write the code.

I made an attempt any way:

Private Sub textBox1_TextChanged(sender As Object, e As EventArgs)
    Dim lineCount As Integer = textBox1.Lines.Count()

    If lineCount > 49 Then
        textBox1.Text = textBox1.Text.Substring(textBox1.Text.IndexOf(Environment.NewLine))
    End If
End Sub

Answer 4

You could try something like this:

If TextBox1.Lines.Count = 50 Then
    Dim temp As String(50)
    Array.Copy(TextBox1.Lines,1,temp,0,49)
    TextBox1.Lines = temp
End If

TextBox1.AppendText(Environment.NewLine & "Current status : " & currentStatus)

I'm running on brain compiler and an iPhone at the moment, but I think that should work.