Class SqlBlobStream

Exposes a Stream around a text, ntext, or image column, supporting both synchronous and asynchronous read and write operations.

Inheritance

System.Object

System.MarshalByRefObject

System.IO.Stream

SqlBlobStream

Implements

System.IDisposable

Inherited Members

System.IO.Stream.Null

System.IO.Stream.CopyToAsync(System.IO.Stream)

System.IO.Stream.CopyToAsync(System.IO.Stream, System.Int32)

System.IO.Stream.CopyToAsync(System.IO.Stream, System.Int32, System.Threading.CancellationToken)

System.IO.Stream.CopyTo(System.IO.Stream)

System.IO.Stream.CopyTo(System.IO.Stream, System.Int32)

System.IO.Stream.Dispose()

System.IO.Stream.Dispose(System.Boolean)

System.IO.Stream.FlushAsync()

System.IO.Stream.FlushAsync(System.Threading.CancellationToken)

System.IO.Stream.CreateWaitHandle()

System.IO.Stream.BeginRead(System.Byte[], System.Int32, System.Int32, System.AsyncCallback, System.Object)

System.IO.Stream.EndRead(System.IAsyncResult)

System.IO.Stream.ReadAsync(System.Byte[], System.Int32, System.Int32)

System.IO.Stream.ReadAsync(System.Byte[], System.Int32, System.Int32, System.Threading.CancellationToken)

System.IO.Stream.BeginWrite(System.Byte[], System.Int32, System.Int32, System.AsyncCallback, System.Object)

System.IO.Stream.EndWrite(System.IAsyncResult)

System.IO.Stream.WriteAsync(System.Byte[], System.Int32, System.Int32)

System.IO.Stream.WriteAsync(System.Byte[], System.Int32, System.Int32, System.Threading.CancellationToken)

System.IO.Stream.ReadByte()

System.IO.Stream.WriteByte(System.Byte)

System.IO.Stream.Synchronized(System.IO.Stream)

System.IO.Stream.ObjectInvariant()

System.IO.Stream.CanTimeout

System.IO.Stream.ReadTimeout

System.IO.Stream.WriteTimeout

System.MarshalByRefObject.MemberwiseClone(System.Boolean)

System.MarshalByRefObject.GetLifetimeService()

System.MarshalByRefObject.InitializeLifetimeService()

System.MarshalByRefObject.CreateObjRef(System.Type)

System.Object.ToString()

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

Namespace: Mediachase.BusinessFoundation.Data.Sql

Assembly: Mediachase.BusinessFoundation.Data.dll

Version: 11.8.3

Syntax

public class SqlBlobStream : Stream, IDisposable

Remarks

A common practice to reduce the amount of memory used when writing a BLOB value is to write the BLOB to the database in "chunks". The process of writing a BLOB to a database in this way depends on the capabilities of your database.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Use the SqlBlobStream class to read, write, create or close text, ntext, or image values from a text, ntext, or image column, as well as to manipulate other file-related operating system handles such as file.

SqlBlobStream objects support random access to files using the Seek method. Seek allows the read/write position to be moved to any position within the file. This is done with byte offset reference point parameters. The byte offset is relative to the seek reference point, which can be the beginning, the current position, or the end of the underlying file, as represented by the three properties of the SeekOrigin class.

For an example of using this class, see the Example section below.

Examples

The following SqlBlobStream constructor grants read-only access to an column (SqlBlobAccess.Read).

string strConnectionString = "Data source=(local);Initial catalog=TestDB;User Id=sa;Password=";
string strSqlTable = "Files";
string strBLOBColumn = "Data";

try
{
	using(SqlBlobStream stream = new SqlBlobStream(strConnectionString,
			strSqlTable,
			strBLOBColumn,
			SqlBlobAccess.Read,new SqlParameter("@FileId",12345)))
	{
		byte[] tmpBuffer = new byte[1024];
		int Length = 0;
		while((Length=stream.Read(buffer,0,1024))==1024)
		{
			//TODO: Save tmpBuffer
		}
	}
}
catch(Exception ex)
{
	System.Diagnostics.Trace.WriteLine(ex);
	throw;
}

Constructors

SqlBlobStream()

Initializes a new instance of SqlBlobStream class.

Declaration

public SqlBlobStream()

Remarks

Invoke Mediachase.FileUploader.SqlBlobStream.Open method to open stream.

SqlBlobStream(String, String, SqlBlobAccess, SqlParameter[])

Initializes a new instance of the SqlBlobStream class.

Declaration

public SqlBlobStream(string TableName, string BlobDataColumn, SqlBlobAccess BlobAccess, params SqlParameter[] PrimaryKeys)

Parameters

Type	Name	Description
System.String	TableName	Name of the table.
System.String	BlobDataColumn	The BLOB data column.
SqlBlobAccess	BlobAccess	The BLOB access.
System.Data.SqlClient.SqlParameter[]	PrimaryKeys	The primary keys.

SqlBlobStream(String, String, SqlBlobAccess, String, Guid)

Initializes a new instance of the SqlBlobStream class.

Declaration

public SqlBlobStream(string TableName, string BlobDataColumn, SqlBlobAccess BlobAccess, string PrimaryKeyColumn, Guid PrimaryKey)

Parameters

Type	Name	Description
System.String	TableName	Name of the table.
System.String	BlobDataColumn	The BLOB data column.
SqlBlobAccess	BlobAccess	The BLOB access.
System.String	PrimaryKeyColumn	The primary key column.
System.Guid	PrimaryKey	The primary key.

SqlBlobStream(String, String, SqlBlobAccess, String, Int32)

Initializes a new instance of the SqlBlobStream class.

Declaration

public SqlBlobStream(string TableName, string BlobDataColumn, SqlBlobAccess BlobAccess, string PrimaryKeyColumn, int PrimaryKey)

Parameters

Type	Name	Description
System.String	TableName	Name of the table.
System.String	BlobDataColumn	The BLOB data column.
SqlBlobAccess	BlobAccess	The BLOB access.
System.String	PrimaryKeyColumn	The primary key column.
System.Int32	PrimaryKey	The primary key.

Properties

BlobAccess

Gets a current read/write permission.

Declaration

public virtual SqlBlobAccess BlobAccess { get; }

Property Value

Type	Description
SqlBlobAccess

CanRead

Overridden. Gets a value indicating whether the current stream supports reading.

Declaration

public override bool CanRead { get; }

Property Value

Type	Description
System.Boolean

Overrides

System.IO.Stream.CanRead

CanSeek

Overridden. Gets a value indicating whether the current stream supports seeking.

Declaration

public override bool CanSeek { get; }

Property Value

Type	Description
System.Boolean

Overrides

System.IO.Stream.CanSeek

CanWrite

Overridden. Gets a value indicating whether the current stream supports writing.

Declaration

public override bool CanWrite { get; }

Property Value

Type	Description
System.Boolean

Overrides

System.IO.Stream.CanWrite

ColumnName

Gets, sets a table column for the BLOB value that the current SqlBlobStream object will encapsulate.

Declaration

public virtual string ColumnName { get; set; }

Property Value

Type	Description
System.String

IsOpen

Gets the current SqlBlobStream's state.

Declaration

public bool IsOpen { get; }

Property Value

Type	Description
System.Boolean

Length

Overridden. Gets the length in bytes of the stream.

Declaration

public override long Length { get; }

Property Value

Type	Description
System.Int64

Overrides

System.IO.Stream.Length

Pointer

Gets a current pointer to the BLOB value.

Declaration

public byte[] Pointer { get; }

Property Value

Type	Description
System.Byte[]

Position

Overridden. Gets or sets the current position of this stream.

Declaration

public override long Position { get; set; }

Property Value

Type	Description
System.Int64

Overrides

System.IO.Stream.Position

PrimaryKeys

Gets the primary keys collection.

Declaration

public virtual SqlParameterList PrimaryKeys { get; }

Property Value

Type	Description
SqlParameterList

TableName

Gets, sets a table name for the table that the current SqlBlobStream object will encapsulate.

Declaration

public virtual string TableName { get; set; }

Property Value

Type	Description
System.String

Methods

Close()

Overridden. Closes the file and releases any resources associated with the current file stream.

Declaration

public override void Close()

Overrides

System.IO.Stream.Close()

Flush()

Overridden. Clears all buffers for this stream and causes any buffered data to be written to the underlying device.

Declaration

public override void Flush()

Overrides

System.IO.Stream.Flush()

GetDataLength()

Gets the selected element's data length.

Declaration

protected virtual int GetDataLength()

Returns

Type	Description
System.Int32	The data length. (bytes)

GetDataLengthCommand()

Gets the sql command returning Data Length.

Declaration

protected virtual string GetDataLengthCommand()

Returns

Type	Description
System.String	The sql command.

GetOpenPointerCommand()

Gets the sql command returning a text pointer.

Declaration

protected virtual string GetOpenPointerCommand()

Returns

Type	Description
System.String	The sql command.

GetReadTextCommand()

Gets the sql command reading a blob element.

Declaration

protected virtual string GetReadTextCommand()

Returns

Type	Description
System.String	The sql command.

GetUpdateTextCommand()

Gets the sql command updating a blob element.

Declaration

protected virtual string GetUpdateTextCommand()

Returns

Type	Description
System.String	The sql command.

GetUpdateTextCommandWithNullValue()

Gets the sql command inserting a blob element.

Declaration

protected virtual string GetUpdateTextCommandWithNullValue()

Returns

Type	Description
System.String	The sql command.

Init()

Initializes a new connection.

Declaration

protected void Init()

OnClose(Boolean)

Releases the resources used by the SqlBlobStream.

Declaration

protected virtual void OnClose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing	The disposing flag.

OnInit()

Raises the Init event.

Declaration

protected virtual void OnInit()

Open()

Opens the closed connection.

Declaration

public void Open()

OpenPointer()

Opens the text pointer.

Declaration

protected virtual byte[] OpenPointer()

Returns

Type	Description
System.Byte[]	The text pointer.

Read(Byte[], Int32, Int32)

Overridden. Reads a block of bytes from the stream and writes the data in a given buffer.

Declaration

public override int Read(byte[] buffer, int offset, int count)

Parameters

Type	Name	Description
System.Byte[]	buffer	When this method returns, contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.
System.Int32	offset	The byte offset in array at which to begin reading.
System.Int32	count	The maximum number of bytes to read.

Returns

Type	Description
System.Int32	The total number of bytes read into the buffer. This might be less than the number of bytes requested if that number of bytes are not currently available, or zero if the end of the stream is reached.

Overrides

System.IO.Stream.Read(System.Byte[], System.Int32, System.Int32)

ReadText(Byte[], Int32, Int32)

Reads the array from the BLOB column.

Declaration

protected virtual int ReadText(byte[] buffer, int offset, int count)

Parameters

Type	Name	Description
System.Byte[]	buffer	When this method returns, contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.
System.Int32	offset	The byte offset in array at which to begin reading.
System.Int32	count	The maximum number of bytes to read.

Returns

Type	Description
System.Int32	The total number of bytes read into the buffer. This might be less than the number of bytes requested if that number of bytes are not currently available, or zero if the end of the stream is reached.

Seek(Int64, SeekOrigin)

Overridden. Sets the current position of this stream to the given value.

Declaration

public override long Seek(long offset, SeekOrigin origin)

Parameters

Type	Name	Description
System.Int64	offset	The point relative to origin from which to begin seeking.
System.IO.SeekOrigin	origin	Specifies the beginning, the end, or the current position as a reference point for origin, using a value of type SeekOrigin.

Returns

Type	Description
System.Int64	The new position in the stream.

Overrides

System.IO.Stream.Seek(System.Int64, System.IO.SeekOrigin)

SetLength(Int64)

Overridden. Sets the length of this stream to the given value.

Declaration

public override void SetLength(long value)

Parameters

Type	Name	Description
System.Int64	value	The new length of the stream.

Overrides

System.IO.Stream.SetLength(System.Int64)

UpdateText(Byte[], Int64, Int64)

Writes the array into the BLOB column.

Declaration

protected virtual void UpdateText(byte[] buffer, long offset, long count)

Parameters

Type	Name	Description
System.Byte[]	buffer	The array to which bytes are written.
System.Int64	offset	The byte offset in array at which to begin writing.
System.Int64	count	The maximum number of bytes to write.

UpdateTextCommandWithNullValue(Byte[], Int64, Int64)

Writes the array into the BLOB column.

Declaration

protected virtual void UpdateTextCommandWithNullValue(byte[] buffer, long offset, long count)

Parameters

Type	Name	Description
System.Byte[]	buffer	The array to which bytes are written.
System.Int64	offset	The byte offset in array at which to begin writing.
System.Int64	count	The maximum number of bytes to write.

Write(Byte[], Int32, Int32)

Overridden. Writes a block of bytes to this stream using data from a buffer.

Declaration

public override void Write(byte[] buffer, int offset, int count)

Parameters

Type	Name	Description
System.Byte[]	buffer	The array to which bytes are written.
System.Int32	offset	The byte offset in array at which to begin writing.
System.Int32	count	The maximum number of bytes to write.

Overrides

System.IO.Stream.Write(System.Byte[], System.Int32, System.Int32)

Implements

System.IDisposable