The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 3: Accessing FILESTREAM Data from Client Applications// Open and read file using SqlFileStream Classstring filePath = reader.GetString(0);object objContext = reader.GetValue(1);byte[] txContext = (byte[])objContext;SqlFileStream fs = new SqlFileStream(filePath, txContext, FileAccess.Read);Listing 3-6:Using C# to open a FILESTREAM data file for read access.The parameter filePath is the logical path name of the FILESTREAM data file weobtained using the PathName() method call, and txContext is the FILESTREAMtransaction context associated with the current transaction.The third parameter specifies the file access mode. It can be one of Read, Write, orReadWrite. Read opens the FILESTREAM data file for reading all the content. WhenWrite is specified, the SqlFileStream object will point to a zero-byte file and existingdata will be overwritten when the object is closed and transaction is committed. WhenReadWrite is used, the file is opened for both reading and writing, and the file pointeris placed at the beginning of the file. By using the Seek() method, you can move the filepointer to any location in the file to overwrite the existing content, or you can move itto the end of the file to append more data. See SqlFileStream Class Reference, later in thischapter, for a detailed discussion of the different constructors and member functions ofthe SqlFileStream class.Non .NET programming languages can use the FILESTREAM Win32 API to obtain aWindows file handle to the requested FILESTREAM data file, and use the file handleto read or write FILESTREAM data. SQL Server 2008, or later, Native Client exposes anew Win32 API, OpenSqlFilestream(), which returns a Windows file handle to therequested FILESTREAM data file. Just like the .NET example we saw earlier, you need topass the FILESTREAM transaction context and logical path to the desired FILESTREAMdata value when calling this function, as shown in Listing 3-7.96