How can I append text to the end a line in a text file with lines already there in VB.NET?
For example my text file looks like this:
header1,header2,header3
value1,value2,value3
stuff1,stuff2,stuff3
and I want to add new text to the end of each line so it looks like this:
header1,header2,header3,newheader
value1,value2,value3,newvalue
stuff1,stuff2,stuff3,newstuff
I know that in Perl you can point to the line and then act on it, is there some VB.net way to do this?
If the file isn't too big, the simplest is, probably, to use the IO.File.ReadAllLines method to read the file into memory and modify the data and write it back with the WriteAllLines method.
For very large files you're probably looking at reading each line modifying it and writing it to a different file.
Related
I need to append 1 text file to another text file.
I've done several keyword searches, and keep coming up with instructions on adding text to an existing file ... which is not the same as appending one text file to another text file.
In a well-designed language, it might look something like the line below, with the contents of source2 added to source1.
Append(path/source1, path/source2, ResultCode)
I have a large file which i am writing to a smaller file in VB, i just dont know how to select lines from an input file that i opened.
I would like to keep the first 12 lines of the large file and them copy every 3rd line into the new output.
Any help?!
You can do this with a StreamReader - just open one on the file, then you can call ReadLine() on it as many times as you need.
Easiest implementation would probably be a 0-to-11 (or 1-to-12) For loop, then a While where you read 2 and ignore them, then read the 3rd and write it.
Writing the new file can be done with StreamWriter, which just has a WriteLine() method to write the text.
The StreamReader and StreamWriter are generally the easiest ways to read and write text files.
I am working on a program with a list box that displays text from a selected text file. I have already made it to delete the item from the listbox but I don't know how to get it to delete that same line from the text file so it doesn't just display it again when you reopen the dialog. Any help? I am using streamwriter and streamreader. I can also TeamView if needed.
The easiest and in most cases best approach is to overwrite the whole file. So you you want to delete all lines that are no longer in the ListBox?
Dim resultLines = From line In IO.File.ReadAllLines(path)
Join item In lb.Items On item.ToString Equals line
Select line
IO.File.WriteAllLines(path, resultLines)
This reads all lines from the file and joins them with the not deleted items in the ListBox. The resulting lines are written back to the file.
The simplest method is to re-write the file using the contents of the listbox. You didn't specify any mapping from the text file to the listbox, so I can't give more detail.
I would like to create a text file with some data i am manipulating in a script component and write it to a text file. i know how to write it to an existing text file, but what i would like to do is create the text file programmatically so i can name it textfile(TodaysDate).txt
How can i do this??
You can call File.CreateText(someString).
This method returns a StreamWriter which can be used to write to the file.
Remember to close the StreamWriter usinga using statement.
If you start with a sample of the text file that you want stored somewhere, you can use a file system task to copy the sample file to the correct name (make sure you copy so that it's still there for tomorrow). Then use an expression to set the file location in the file connection manager.
I have a CPP file. I am using VB in VS2005. I have opened that file using the FileSystemObject. I am reading each and every line in that CPP file. I have to comment all the lines until I encounter a return statement. I am using the scripting.textstream to read a line from the CPP file. But I have no idea as to how we can add a // comment to the beginning of every line that I read or even a multiline comment from the beginning till a return statement. Please help.
You seem to be using the FileSystemObject of the Windows script runtime instead of the System.IO.File class's methods. Strange!
The static System.IO.File.ReadAllLines() will read a file (and close it) and return a string array containing all the lines. You could then iterate through the array and add a comment to each line (except if the line starts with return).
Finally, save the changed text to the file using any of the WriteAllLines() method, thus overwriting any contained text.
Adding a multiline comment at the start would be even easier, you would not need to read the lines into an array.