Zip and unzip file using vb.net

The following figure shows the Add Reference dialog of Visual Studio with this assembly selected. The java. Finally, the java. The classes that we will use from the above namespaces are :.

A ZipFile contains zero or more ZipEntry objects and actual content of the zipped files. Each entry is nothing but metadata about a zipped file. Finally, the Enumeration class is J way to represent collections. Before we actually write code to create or extract ZIP files let's create some helper methods that we need later. We need to create the following helper methods:.

The GetZippedItems method is shown below:. The method creates a generic collection of ZipEntry type. The code then iterates through the enumeration and populates the List. Finally, the populated List is returned to the caller. While adding or removing files from an existing ZIP file we need to copy contents of constituent files from source to destination streams. Hence, we need a helper method called CopyStreams to do that job.

The CopyStreams method is shown below:. The CopyStream method accepts source and destination streams in the form of InputStream and OutputStream objects respectively. It then reads the source stream using read method.

The read method reads data in chunks of sbytes signed integer and writes it to the destination stream using write method of OutputStream class. The J compression classes do not allow you to add or remove files from an existing ZIP file. CopyEntries is such a method. The CopyEntries method has two overloads as shown below:. The first overload of CopyEntries method accepts two parameters. The first parameter is the source ZipFile from which entries are to be copied.

The second parameter is the target ZipOutputStream to which the entries are to be written. The second overload of CopyEntries method is intended to copy only certain entries and accepts three parameters. The significance of the first two parameters is the same as before. The third parameter is an array of entry names that are to be copied to the destination ZipOutputStream.

The entries are then transferred to the ZipOutputStream. You may need to add a reference in Visual Studio. Go to Add Reference and select System. ZipFile was not in the older versions of. Compression levels. The Optimal compression level helps reduce the size of the archive.

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Let's work to help developers, not make them feel stupid. Related Questions. How to extract an embeded zip file in resources. If the archive already exists, an IOException is thrown.

When you set the mode parameter to Update , the archive is opened with FileMode. OpenOrCreate as the file mode value. If the archive exists, it is opened. The existing entries can be modified and new entries can be created. If the archive does not exist, a new archive is created; however, creating a zip archive in Update mode is not as efficient as creating it in Create mode.

One of the enumeration values that specifies the actions that are allowed on the entries in the opened archive. The encoding to use when reading or writing entry names in this archive. Specify a value for this parameter only when an encoding is required for interoperability with zip archive tools and libraries that do not support UTF-8 encoding for entry names.

When you set the mode parameter to Read , the archive is opened with FileMode. Open as the file mode value. When you open a zip archive file for reading and entryNameEncoding is set to null , entry names are decoded according to the following rules:.