Replacing multiple lines in a textfile in VB 2017 - vb.net

Question

I'm stuck a little here, what I want to do is read a text file find the lines that contain X= and Y= and change X= to X=1 and Y= to Y=1
So far I got this code
Dim MyPath As String = "C:\Users\kiko4\Desktop\text.txt"
Dim Rdr As New StreamReader(MyPath)
Dim ln As String
Dim NewFile As New StringBuilder
ln = Rdr.ReadLine
Do Until ln Is Nothing
If ln.StartsWith("X=", "Y=") And ComboBox1.Text = "1" Then ln = "X=1" & "Y=1"
NewFile.AppendLine(ln)
ln = Rdr.ReadLine
Loop
Rdr.Close()
File.WriteAllText(MyPath, NewFile.ToString)
MsgBox("Successfully changed the resolution.", MsgBoxStyle.Information)
End Sub
So this results to only changing X and leaving Y like it is, is it possible to change the two lines at the same time?

Answer 1

Try going for a different approach when you're stuck... try this :
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim SR As New StreamReader("C:\Users\kiko4\Desktop\text.txt")
Dim Result As String = SR.ReadToEnd()
SR.Close()
Dim Lines As String() = Result.Split(Environment.NewLine)
Dim TestLine As String
Dim ReplacedLine As String
For Each line As String In Lines
TestLine = line
If TestLine.Contains("X=") Then
ReplacedLine = TestLine.Replace("X=", "X=" & ComboBox1.Text)
Result = Result.Replace(TestLine, ReplacedLine)
ElseIf TestLine.Contains("Y=") Then
ReplacedLine = TestLine.Replace("Y=", "Y=" & ComboBox1.Text)
Result = Result.Replace(TestLine, ReplacedLine)
End If
Next
Dim SW As New StreamWriter("C:\Users\kiko4\Desktop\text.txt")
SW.Write(Result)
SW.Close()
End Sub
Please feel free to ask about anything you didn't understand.
Hope that was useful

Answer 2

Using StreamReaders/Writers is nice and all, and it surely is the best approach
when you are trying to iterate over multiple lines, one by one.
However, in this case this really isn't neccessary, since OP's just trying to replace all occurences within the file, lines do not matter at all.
From a readability/length perspective, something like this would be preferable:
Dim inPath As String = "C:\Users\kiko4\Desktop\text.txt"
Dim trText As String = File.ReadAllText(inPath)
If trText.Contains("X=") AndAlso trText.Contains("Y=") Then File.WriteAllText(inPath, trText.Replace("X=", "X=1").Replace("Y=", "Y=1"))
(all text in the file is read and saved as a single string to trText, if trText contains the string to be replaced write the contents of trText with replaced values to the file)
Or, if you are 100% sure that every file passed will contain the search-values, you can even do it in one Line:
File.WriteAllText("C:\Users\kiko4\Desktop\text.txt", File.ReadAllText("C:\Users\kiko4\Desktop\text.txt").Replace("X=", "X=1").Replace("Y=", "Y=1"))
This one will blow up if the file doesn't contain "X=" AND "Y=".

Answer 3

This is how I fixed it, works as i intended to, which changes both values, thanks everyone for their help :)
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim MyPath As String "C:\Users\kiko4\AppData\Local\FortniteGame\Saved\Config\WindowsClient\text.txt")
Dim Rdr As New StreamReader(MyPath)
Dim ln As String
Dim ac As String
Dim NewFile As New StringBuilder
ln = Rdr.ReadLine
ac = Rdr.ReadLine
Do Until ln Is Nothing
If ln.StartsWith("ResolutionSizeX=") Then ln = "ResolutionSizeX=" + TextBox1.Text
NewFile.AppendLine(ln)
ln = Rdr.ReadLine
If ac.StartsWith("ResolutionSizeY=") Then ac = "ResolutionSizeY=" + TextBox2.Text
NewFile.AppendLine(ac)
ac = Rdr.ReadLine
Loop
Rdr.Close()
File.WriteAllText(MyPath, NewFile.ToString)
MsgBox("Successfully changed the resolution.", MsgBoxStyle.Information)
End Sub
End Class