StreamWriter writes data to a text file. It can write lines of text or strings to the file. It is easy to use, and one of the most common classes in VB.NET programs.
Ideal usage. Ideally StreamWriter should be used inside a VB.NET Using statement. This ensures the correct disposal of its resources. The syntax is clear and simple.
Example. Here we use StreamWriter to create a new file, and then write 2 lines of text to it along with 2 newlines. Note how the System.IO namespace is imported at the top.
Start The StreamWriter is instantiated and the file "myfile.txt" is opened for writing. You can change the path to another location.
Next The Write call and the two WriteLine calls write the three Strings to the file. The file's contents are listed in the comment.
Imports System.IO
Module Module1
Sub Main()
Using writer As StreamWriter =
New StreamWriter("myfile.txt")
writer.Write("One ")
writer.WriteLine("two 2")
writer.WriteLine("Three")
End Using
End Sub
End ModuleOne two 2
Three
Append text. Here we use StreamWriter to append lines of text to a file. This is more efficient than reading in the entire file—only the last part of the file needs to be accessed.
Argument 1 The first part of the example opens the file at the absolute path "C:\append.txt".
Argument 2 The second argument to the StreamWriter constructor is the Boolean True. This specifies the append overload.
Then The file is opened again, and a second line is appended to it. The text file contents are shown in the final comment.
Imports System.IO
Module Module1
Sub Main()
' Append the first line of text to a new file.
Using writer As StreamWriter =
New StreamWriter("C:\append.txt", True)
writer.WriteLine("First line appended; 1")
End Using
' Append the second line.
Using writer As StreamWriter =
New StreamWriter("C:\append.txt", True)
writer.WriteLine("Second line appended; 2")
End Using
End Sub
End ModuleFirst line appended; 1
Second line appended; 2
For-loop. Here we use a For-loop with StreamWriter. When you have to loop and add text to a file, you should reuse a single StreamWriter—this improves performance.
Imports System.IO
Module Module1
Sub Main()
' Create new file.
Using writer As StreamWriter =
New StreamWriter("loop.txt")
' Loop through ten numbers.
Dim i As Integer
For i = 0 To 10 - 1
' Write number with format string.
writer.Write("{0:0.0} ", i)
Next i
End Using
End Sub
End Module0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
Encodings. You need to specify the encoding of your target file in the StreamWriter constructor if it is not the default UTF8. Internally, StreamWriter specifies UTF8 by default.
Functions. StreamWriter in VB.NET has a few more Functions on it. For example, the Close and Dispose calls are occasionally useful, but not if you use the Using statement.
Tip If you are not employing the Using construct in VB.NET, make sure to always call Close and Dispose.
Note The Using statement is implemented with Finally logic. This ensures cleanup always occurs.
Summary. Here we saw examples of using StreamWriter in VB.NET. This is an easy way to write to files in the .NET platform. The Using statement is an essential part of the type.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Mar 21, 2023 (edit).