Imported from ScrewTurn Wiki page SharpZipLib_Updating.00000

Updating.md

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+**How to use SharpZipLib to update Zip files**
+
+This page shows how to update an existing zip file. Contents may be added, overwritten or deleted. 
+
+
+# Basic updating of a zip file
+
+First example shows how to add or overwrite entries in a zip file on disk.
+This concentrates on the essentials.
+
+    
+    using ICSharpCode.SharpZipLib.Zip;
+    
+    public void UpdateExistingZip() {
+    	ZipFile zipFile = new ZipFile(@"c:\temp\existing.zip");
+    
+    	// Must call BeginUpdate to start, and CommitUpdate at the end.
+    	zipFile.BeginUpdate();
+    
+    	zipFile.Password = "whatever"; // Only if a password is wanted on the new entry
+    
+    	// The "Add()" method will add or overwrite as necessary.
+    	// When the optional entryName parameter is omitted, the entry will be named
+    	// with the full folder path and without the drive e.g. "temp/folder/test1.txt".
+    	//
+    	zipFile.Add(@"c:\temp\folder\test1.txt");
+    
+    	// Specify the entryName parameter to modify the name as it appears in the zip.
+    	//
+    	zipFile.Add(@"c:\temp\folder\test2.txt", "test2.txt");
+    
+    	// Continue calling .Add until finished.
+    
+    	// Both CommitUpdate and Close must be called.
+    	zipFile.CommitUpdate();
+    	zipFile.Close();
+    }
+
+
+
+
+# Updating a zip file in memory
+
+Updating in memory is no more difficult than updating a disk file. The only real difference is setting IsStreamOwner. 
+
+    
+    // This will update a zip file contained in a memory stream.
+    public void UpdateZipInMemory(MemoryStream ms) {
+    
+    	// The memorystream is expected to contain the complete zipfile
+    	ZipFile zipFile = new ZipFile(ms);
+    
+    	zipFile.BeginUpdate();
+    
+    	zipFile.Add(@"c:\temp\folder\test1.txt"); // Default naming
+    	zipFile.Add(@"c:\temp\folder\test2.txt", "test2.txt"); // Explicit naming
+    	// etc
+    
+    	// Both CommitUpdate and Close must be called.
+    	zipFile.CommitUpdate();
+    	// Set this so that Close does not close the memorystream
+    	zipFile.IsStreamOwner = false;
+    	zipFile.Close();
+    
+    	// Reposition to the start for the convenience of the caller.
+    	ms.Position = 0;
+    }
+    // This is a test harnesss to check that the update in memory is working.
+    //
+    public void CallingExample() {
+    
+    	// Read a disk file into memory
+    	MemoryStream ms = new MemoryStream();
+    	FileStream fs = File.OpenRead(@"c:\temp\existing.zip");
+    
+    	// Copying whole file into a byte array is not efficient. Better to use StreamUtils.Copy as shown below.
+    	byte[ ] bytes = new byte[fs.Length];
+    	fs.Read(bytes, 0, (int)fs.Length);
+    	fs.Close();
+    	ms.Write(bytes, 0, bytes.Length);
+    
+    	// Do the update
+    	UpdateZipInMemory(ms);
+    
+    	// Save the update to disk
+    	fs = File.Create(@"c:\temp\updated.zip");
+    	// This utility method copies from stream to stream.
+    	ICSharpCode.SharpZipLib.Core.StreamUtils.Copy(ms, fs, new byte[4096]);
+    	fs.Close();
+    }
+
+
+[[Back to Code Reference main page|Code Reference]]