How do I save a stream to a file in C

Question

I have a StreamReader object that I initialized with a stream  now I want to save this stream to disk  the stream may be a  gif or  jpg or  pdf    Existing Code   StreamReader sr   new StreamReader myOtherObject InputStream      I need to save this to disk  I have the filename   In the future I may want to store this to SQL Server    I have the encoding type also  which I will need if I store it to SQL Server  correct

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public void CopyStream Stream stream  string destPath      using  var fileStream   new FileStream destPath  FileMode Create  FileAccess Write           stream CopyTo fileStream

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I don t get all of the answers using CopyTo  where maybe the systems using the app might not have been upgraded to  NET 4 0    I know some would like to force people to upgrade  but compatibility is also nice  too   Another thing  I don t get using a stream to copy from another stream in the first place   Why not just do   byte   bytes   myOtherObject InputStream ToArray      Once you have the bytes  you can easily write them to a file   public static void WriteFile string fileName  byte   bytes        string path   Path GetDirectoryName Assembly GetExecutingAssembly   Location       if   path EndsWith        path               if  File Exists Path Combine path  fileName            File Delete Path Combine path  fileName         using  FileStream fs   new FileStream Path Combine path  fileName   FileMode CreateNew  FileAccess Write                 fs Write bytes  0   int bytes Length             fs Close              This code works as I ve tested it with a  jpg file  though I admit I have only used it with small files  less than 1 MB    One stream  no copying between streams  no encoding needed  just write the bytes   No need to over-complicate things with StreamReader if you already have a stream you can convert to bytes directly with  ToArray       Only potential downsides I can see in doing it this way is if there s a large file you have  having it as a stream and using  CopyTo   or equivalent allows FileStream to stream it instead of using a byte array and reading the bytes one by one   It might be slower doing it this way  as a result   But it shouldn t choke since the  Write   method of the FileStream handles writing the bytes  and it s only doing it one byte at a time  so it won t clog memory  except that you will have to have enough memory to hold the stream as a byte   object   In my situation where I used this  getting an OracleBlob  I had to go to a byte    it was small enough  and besides  there was no streaming available to me  anyway  so I just sent my bytes to my function  above   Another option  using a stream  would be to use it with Jon Skeet s CopyStream function that was in another post - this just uses FileStream to take the input stream and create the file from it directly   It does not use File Create  like he did  which initially seemed to be problematic for me  but later found it was likely just a VS bug            lt summary gt      Copies the contents of input to output  Doesn t close either stream       lt  summary gt  public static void CopyStream Stream input  Stream output        byte   buffer   new byte 8   1024       int len      while    len   input Read buffer  0  buffer Length    gt  0                output Write buffer  0  len                public static void WriteFile string fileName  Stream inputStream        string path   Path GetDirectoryName Assembly GetExecutingAssembly   Location       if   path EndsWith        path               if  File Exists Path Combine path  fileName            File Delete Path Combine path  fileName         using  FileStream fs   new FileStream Path Combine path  fileName   FileMode CreateNew  FileAccess Write                CopyStream inputStream  fs              inputStream Close        inputStream Flush

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You must not use StreamReader for binary files  like gifs or jpgs   StreamReader is for text data  You will almost certainly lose data if you use it for arbitrary binary data   If you use Encoding GetEncoding 28591  you will probably be okay  but what s the point    Why do you need to use a StreamReader at all  Why not just keep the binary data as binary data and write it back to disk  or SQL  as binary data   EDIT  As this seems to be something people want to see    if you do just want to copy one stream to another  e g  to a file  use something like this        lt summary gt      Copies the contents of input to output  Doesn t close either stream       lt  summary gt  public static void CopyStream Stream input  Stream output        byte   buffer   new byte 8   1024       int len      while    len   input Read buffer  0  buffer Length    gt  0                output Write buffer  0  len                 To use it to dump a stream to a file  for example   using  Stream file   File Create filename         CopyStream input  file       Note that Stream CopyTo was introduced in  NET 4  serving basically the same purpose

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You must not use StreamReader for binary files  like gifs or jpgs   StreamReader is for text data  You will almost certainly lose data if you use it for arbitrary binary data   If you use Encoding GetEncoding 28591  you will probably be okay  but what s the point    Why do you need to use a StreamReader at all  Why not just keep the binary data as binary data and write it back to disk  or SQL  as binary data   EDIT  As this seems to be something people want to see    if you do just want to copy one stream to another  e g  to a file  use something like this        lt summary gt      Copies the contents of input to output  Doesn t close either stream       lt  summary gt  public static void CopyStream Stream input  Stream output        byte   buffer   new byte 8   1024       int len      while    len   input Read buffer  0  buffer Length    gt  0                output Write buffer  0  len                 To use it to dump a stream to a file  for example   using  Stream file   File Create filename         CopyStream input  file       Note that Stream CopyTo was introduced in  NET 4  serving basically the same purpose

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If you don t have  Net 4 0      public void SaveStreamToFile Stream stream  string filename         using Stream destination   File Create filename         Write stream  destination        Typically I implement this Write method as a Stream extension method     The framework handles buffering   public void Write Stream from  Stream to       for int a   from ReadByte    a    -1  a   from ReadByte          to WriteByte   byte  a          Note  StreamReader is an IEnumerable lt Char gt  while Stream is an IEnumbable lt byte gt   The distinction is significant such as in multiple byte character encodings  like Unicode used in  Net where Char is one or more bytes  byte n    Also  the resulting translation from IEnumerable lt byte gt  to IEnumerable lt Char gt  can loose bytes or insert them  for example    n  vs    r n   depending on the StreamReader instance CurrentEncoding

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private void SaveFileStream String path  Stream stream        var fileStream   new FileStream path  FileMode Create  FileAccess Write       stream CopyTo fileStream       fileStream Dispose

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Another option is to get the stream to a byte   and use File WriteAllBytes  This should do   using  var stream   new MemoryStream          input CopyTo stream       File WriteAllBytes file  stream ToArray         Wrapping it in an extension method gives it better naming   public void WriteTo this Stream input  string file          your fav write method       using  var stream   File Create file                 input CopyTo stream                or      using  var stream   new MemoryStream                  input CopyTo stream           File WriteAllBytes file  stream ToArray                  whatever that fits

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public void CopyStream Stream stream  string destPath      using  var fileStream   new FileStream destPath  FileMode Create  FileAccess Write           stream CopyTo fileStream

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If you don t have  Net 4 0      public void SaveStreamToFile Stream stream  string filename         using Stream destination   File Create filename         Write stream  destination        Typically I implement this Write method as a Stream extension method     The framework handles buffering   public void Write Stream from  Stream to       for int a   from ReadByte    a    -1  a   from ReadByte          to WriteByte   byte  a          Note  StreamReader is an IEnumerable lt Char gt  while Stream is an IEnumbable lt byte gt   The distinction is significant such as in multiple byte character encodings  like Unicode used in  Net where Char is one or more bytes  byte n    Also  the resulting translation from IEnumerable lt byte gt  to IEnumerable lt Char gt  can loose bytes or insert them  for example    n  vs    r n   depending on the StreamReader instance CurrentEncoding

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Here s an example that uses proper usings and implementation of idisposable  static void WriteToFile string sourceFile  string destinationfile  bool append   true  int bufferSize   4096        using  var sourceFileStream   new FileStream sourceFile  FileMode OpenOrCreate                 using  var destinationFileStream   new FileStream destinationfile  FileMode OpenOrCreate                         while  sourceFileStream Position  lt  sourceFileStream Length                                destinationFileStream WriteByte  byte sourceFileStream ReadByte                                         and there s also this     public static void WriteToFile Stream stream  string destinationFile  int bufferSize   4096  FileMode mode   FileMode OpenOrCreate  FileAccess access   FileAccess ReadWrite  FileShare share   FileShare ReadWrite                using  var destinationFileStream   new FileStream destinationFile  mode  access  share                         while  stream Position  lt  stream Length                                 destinationFileStream WriteByte  byte stream ReadByte                                    The key is understanding the proper use of using  which should be implemented on the instantiation of the object that implements idisposable as shown above   and having a good idea as to how the properties work for streams  Position is literally the index within the stream  which starts at 0  that is followed as each byte is read using the readbyte method  In this case I am essentially using it in place of a for loop variable and simply letting it follow through all the way up to the length which is LITERALLY the end of the entire stream  in bytes   Ignore in bytes because it is practically the same and you will have something simple and elegant like this that resolves everything cleanly  Keep in mind  too  that the ReadByte method simply casts the byte to an int in the process and can simply be converted back  I m gonna add another implementation I recently wrote to create a dynamic buffer of sorts to ensure sequential data writes to prevent massive overload private void StreamBuffer Stream stream  int buffer        using  var memoryStream   new MemoryStream                  stream CopyTo memoryStream           var memoryBuffer   memoryStream GetBuffer             for  int i   0  i  lt  memoryBuffer Length                         var networkBuffer   new byte buffer               for  int j   0  j  lt  networkBuffer Length  amp  amp  i  lt  memoryBuffer Length  j                                  networkBuffer j    memoryBuffer i                   i                                Assuming destination file             destinationFileStream Write networkBuffer  0  networkBuffer Length                      The explanation is fairly simple  we know that we need to keep in mind the entire set of data we wish to write and also that we only want to write certain amounts  so we want the first loop with the last parameter empty  same as while   Next  we  initialize a byte array buffer that is set to the size of what s passed  and with the second loop we compare j to the size of the buffer and the size of the original one  and if it s greater than the size of the original byte array  end the run

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public void testdownload stream input        byte   buffer   new byte 16345       using  FileStream fs   new FileStream this FullLocalFilePath                          FileMode Create  FileAccess Write  FileShare None                 int read          while   read   input Read buffer  0  buffer Length    gt  0                         fs Write buffer  0  read

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private void SaveFileStream String path  Stream stream        var fileStream   new FileStream path  FileMode Create  FileAccess Write       stream CopyTo fileStream       fileStream Dispose

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I don t get all of the answers using CopyTo  where maybe the systems using the app might not have been upgraded to  NET 4 0    I know some would like to force people to upgrade  but compatibility is also nice  too   Another thing  I don t get using a stream to copy from another stream in the first place   Why not just do   byte   bytes   myOtherObject InputStream ToArray      Once you have the bytes  you can easily write them to a file   public static void WriteFile string fileName  byte   bytes        string path   Path GetDirectoryName Assembly GetExecutingAssembly   Location       if   path EndsWith        path               if  File Exists Path Combine path  fileName            File Delete Path Combine path  fileName         using  FileStream fs   new FileStream Path Combine path  fileName   FileMode CreateNew  FileAccess Write                 fs Write bytes  0   int bytes Length             fs Close              This code works as I ve tested it with a  jpg file  though I admit I have only used it with small files  less than 1 MB    One stream  no copying between streams  no encoding needed  just write the bytes   No need to over-complicate things with StreamReader if you already have a stream you can convert to bytes directly with  ToArray       Only potential downsides I can see in doing it this way is if there s a large file you have  having it as a stream and using  CopyTo   or equivalent allows FileStream to stream it instead of using a byte array and reading the bytes one by one   It might be slower doing it this way  as a result   But it shouldn t choke since the  Write   method of the FileStream handles writing the bytes  and it s only doing it one byte at a time  so it won t clog memory  except that you will have to have enough memory to hold the stream as a byte   object   In my situation where I used this  getting an OracleBlob  I had to go to a byte    it was small enough  and besides  there was no streaming available to me  anyway  so I just sent my bytes to my function  above   Another option  using a stream  would be to use it with Jon Skeet s CopyStream function that was in another post - this just uses FileStream to take the input stream and create the file from it directly   It does not use File Create  like he did  which initially seemed to be problematic for me  but later found it was likely just a VS bug            lt summary gt      Copies the contents of input to output  Doesn t close either stream       lt  summary gt  public static void CopyStream Stream input  Stream output        byte   buffer   new byte 8   1024       int len      while    len   input Read buffer  0  buffer Length    gt  0                output Write buffer  0  len                public static void WriteFile string fileName  Stream inputStream        string path   Path GetDirectoryName Assembly GetExecutingAssembly   Location       if   path EndsWith        path               if  File Exists Path Combine path  fileName            File Delete Path Combine path  fileName         using  FileStream fs   new FileStream Path Combine path  fileName   FileMode CreateNew  FileAccess Write                CopyStream inputStream  fs              inputStream Close        inputStream Flush

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You must not use StreamReader for binary files  like gifs or jpgs   StreamReader is for text data  You will almost certainly lose data if you use it for arbitrary binary data   If you use Encoding GetEncoding 28591  you will probably be okay  but what s the point    Why do you need to use a StreamReader at all  Why not just keep the binary data as binary data and write it back to disk  or SQL  as binary data   EDIT  As this seems to be something people want to see    if you do just want to copy one stream to another  e g  to a file  use something like this        lt summary gt      Copies the contents of input to output  Doesn t close either stream       lt  summary gt  public static void CopyStream Stream input  Stream output        byte   buffer   new byte 8   1024       int len      while    len   input Read buffer  0  buffer Length    gt  0                output Write buffer  0  len                 To use it to dump a stream to a file  for example   using  Stream file   File Create filename         CopyStream input  file       Note that Stream CopyTo was introduced in  NET 4  serving basically the same purpose

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As highlighted by Tilendor in Jon Skeet s answer  streams have a CopyTo method since  NET 4   var fileStream   File Create  C   Path  To  File    myOtherObject InputStream Seek 0  SeekOrigin Begin   myOtherObject InputStream CopyTo fileStream   fileStream Close      Or with the using syntax   using  var fileStream   File Create  C   Path  To  File          myOtherObject InputStream Seek 0  SeekOrigin Begin       myOtherObject InputStream CopyTo fileStream

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Why not use a FileStream object   public void SaveStreamToFile string fileFullPath  Stream stream        if  stream Length    0  return          Create a FileStream object to write a stream to a file     using  FileStream fileStream   System IO File Create fileFullPath   int stream Length                    Fill the bytes   array with the stream data         byte   bytesInStream   new byte stream Length           stream Read bytesInStream  0   int bytesInStream Length               Use FileStream object to write to the specified file         fileStream Write bytesInStream  0  bytesInStream Length

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Another option is to get the stream to a byte   and use File WriteAllBytes  This should do   using  var stream   new MemoryStream          input CopyTo stream       File WriteAllBytes file  stream ToArray         Wrapping it in an extension method gives it better naming   public void WriteTo this Stream input  string file          your fav write method       using  var stream   File Create file                 input CopyTo stream                or      using  var stream   new MemoryStream                  input CopyTo stream           File WriteAllBytes file  stream ToArray                  whatever that fits

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As highlighted by Tilendor in Jon Skeet s answer  streams have a CopyTo method since  NET 4   var fileStream   File Create  C   Path  To  File    myOtherObject InputStream Seek 0  SeekOrigin Begin   myOtherObject InputStream CopyTo fileStream   fileStream Close      Or with the using syntax   using  var fileStream   File Create  C   Path  To  File          myOtherObject InputStream Seek 0  SeekOrigin Begin       myOtherObject InputStream CopyTo fileStream

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Why not use a FileStream object   public void SaveStreamToFile string fileFullPath  Stream stream        if  stream Length    0  return          Create a FileStream object to write a stream to a file     using  FileStream fileStream   System IO File Create fileFullPath   int stream Length                    Fill the bytes   array with the stream data         byte   bytesInStream   new byte stream Length           stream Read bytesInStream  0   int bytesInStream Length               Use FileStream object to write to the specified file         fileStream Write bytesInStream  0  bytesInStream Length

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Here s an example that uses proper usings and implementation of idisposable  static void WriteToFile string sourceFile  string destinationfile  bool append   true  int bufferSize   4096        using  var sourceFileStream   new FileStream sourceFile  FileMode OpenOrCreate                 using  var destinationFileStream   new FileStream destinationfile  FileMode OpenOrCreate                         while  sourceFileStream Position  lt  sourceFileStream Length                                destinationFileStream WriteByte  byte sourceFileStream ReadByte                                         and there s also this     public static void WriteToFile Stream stream  string destinationFile  int bufferSize   4096  FileMode mode   FileMode OpenOrCreate  FileAccess access   FileAccess ReadWrite  FileShare share   FileShare ReadWrite                using  var destinationFileStream   new FileStream destinationFile  mode  access  share                         while  stream Position  lt  stream Length                                 destinationFileStream WriteByte  byte stream ReadByte                                    The key is understanding the proper use of using  which should be implemented on the instantiation of the object that implements idisposable as shown above   and having a good idea as to how the properties work for streams  Position is literally the index within the stream  which starts at 0  that is followed as each byte is read using the readbyte method  In this case I am essentially using it in place of a for loop variable and simply letting it follow through all the way up to the length which is LITERALLY the end of the entire stream  in bytes   Ignore in bytes because it is practically the same and you will have something simple and elegant like this that resolves everything cleanly  Keep in mind  too  that the ReadByte method simply casts the byte to an int in the process and can simply be converted back  I m gonna add another implementation I recently wrote to create a dynamic buffer of sorts to ensure sequential data writes to prevent massive overload private void StreamBuffer Stream stream  int buffer        using  var memoryStream   new MemoryStream                  stream CopyTo memoryStream           var memoryBuffer   memoryStream GetBuffer             for  int i   0  i  lt  memoryBuffer Length                         var networkBuffer   new byte buffer               for  int j   0  j  lt  networkBuffer Length  amp  amp  i  lt  memoryBuffer Length  j                                  networkBuffer j    memoryBuffer i                   i                                Assuming destination file             destinationFileStream Write networkBuffer  0  networkBuffer Length                      The explanation is fairly simple  we know that we need to keep in mind the entire set of data we wish to write and also that we only want to write certain amounts  so we want the first loop with the last parameter empty  same as while   Next  we  initialize a byte array buffer that is set to the size of what s passed  and with the second loop we compare j to the size of the buffer and the size of the original one  and if it s greater than the size of the original byte array  end the run

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public void testdownload stream input        byte   buffer   new byte 16345       using  FileStream fs   new FileStream this FullLocalFilePath                          FileMode Create  FileAccess Write  FileShare None                 int read          while   read   input Read buffer  0  buffer Length    gt  0                         fs Write buffer  0  read

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You must not use StreamReader for binary files  like gifs or jpgs   StreamReader is for text data  You will almost certainly lose data if you use it for arbitrary binary data   If you use Encoding GetEncoding 28591  you will probably be okay  but what s the point    Why do you need to use a StreamReader at all  Why not just keep the binary data as binary data and write it back to disk  or SQL  as binary data   EDIT  As this seems to be something people want to see    if you do just want to copy one stream to another  e g  to a file  use something like this        lt summary gt      Copies the contents of input to output  Doesn t close either stream       lt  summary gt  public static void CopyStream Stream input  Stream output        byte   buffer   new byte 8   1024       int len      while    len   input Read buffer  0  buffer Length    gt  0                output Write buffer  0  len                 To use it to dump a stream to a file  for example   using  Stream file   File Create filename         CopyStream input  file       Note that Stream CopyTo was introduced in  NET 4  serving basically the same purpose

[c#] How do I save a stream to a file in C#?

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