GetBytes(Int32,Int64,Byte[],Int32,Int32) Method

In This Topic

Syntax
Remarks
Example
Requirements
See Also

Reads a stream of bytes from the specified column offset into the buffer as an array starting at the given buffer offset.

Syntax

Visual Basic
C#

public override long GetBytes( 
   int i,
   long fieldOffset,
   byte[] buffer,
   int bufferOffset,
   int length
)

'Declaration
 
Public Overloads Overrides Function GetBytes( _
   ByVal i As Integer, _
   ByVal fieldOffset As Long, _
   ByVal buffer() As Byte, _
   ByVal bufferOffset As Integer, _
   ByVal length As Integer _
) As Long

Parameters

i: The zero-based column ordinal.
fieldOffset: The index within the field where the read operation is to begin.
buffer: The buffer into which to read the stream of bytes.
bufferOffset: The index where buffer is to begin the write operation.
length: The maximum length to copy into the buffer.

Return Value

The actual number of bytes read.

Remarks

GetBytes returns the number of available bytes in the field. In most cases this is the exact length of the field. However, the number returned may be less than the true length of the field if GetBytes has already been used to obtain bytes from the field. This may be the case, for example, if the UniDataReader is reading a large data structure into a buffer.

If you pass a buffer that is a null value, GetBytes returns the length of the field in bytes.

Example

This sample shows how to obtain array of bytes from a table and save it to a file.

csharp

static void GetThatBytes(UniConnection myConnection)
{
  UniCommand cmd = new UniCommand("SELECT * FROM Test.Dept");
  cmd.Connection = myConnection;
  myConnection.Open();
  try
  {
    UniDataReader reader = cmd.ExecuteReader();
    reader.Read();
    byte[] myBytes = new byte[50];
    long bytesRead = reader.GetBytes(reader.GetOrdinal("DName"),0,myBytes,0,50);
    FileStream fs = new FileStream("D:\\Tmp\\1.txt", FileMode.Create);
    fs.Write(myBytes,0,(int)bytesRead);
    fs.Close();
    Console.WriteLine(bytesRead+ " bytes downloaded from table to file.");
    reader.Close();
  }
  finally
  {
    myConnection.Close();
  }
}

Visual Basic

Public Sub GetThatBytes(ByVal myConnection As UniConnection)
  Dim cmd As UniCommand = New UniCommand("SELECT * FROM Test.Dept")
  cmd.Connection = myConnection
  myConnection.Open()
  Try
    Dim reader As UniDataReader = cmd.ExecuteReader()
    reader.Read()
    Dim myBytes(50) As Byte
    Dim bytesRead As Long = reader.GetBytes(reader.GetOrdinal("DName"), 0, myBytes, 0, 50)
    Dim fs As FileStream = New FileStream("D:\Tmp\1.txt", FileMode.Create)
    fs.Write(myBytes, 0, Convert.ToInt32(bytesRead))
    fs.Close()
    Console.WriteLine(bytesRead & " bytes downloaded from table to file.")
    reader.Close()
  Finally
    myConnection.Close()
  End Try
End Sub

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

UniDataReader Class
UniDataReader Members
Overload List

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