SQLiteBlob Class

In This Topic

Represents a variable-length stream of binary data to be stored in or retrieved from a database.

Syntax

Visual Basic
C#

'Declaration
 
Public Class SQLiteBlob 
   Inherits System.IO.Stream
   Implements System.Data.SqlTypes.INullable, System.ICloneable, System.IDisposable, System.Xml.Serialization.IXmlSerializable

public class SQLiteBlob : System.IO.Stream, System.Data.SqlTypes.INullable, System.ICloneable, System.IDisposable, System.Xml.Serialization.IXmlSerializable

Remarks

SQLiteBlob is used to insert or retrieve BLOB fields in databases.

Example

In this example two functions are presented. First can upload a file onto a server, and second can retrieve a BLOB field and paste it into a file. Notice that two classes used here (BinaryWriter and BinaryReader) to provide more flexible stream manipulation are actually redundant for simple data transfer operations.

csharp

public void DownloadBlob(SQLiteConnection sqConnection)
{
  SQLiteCommand sqCommand = new SQLiteCommand("SELECT * FROM Pictures", sqConnection);
  sqConnection.Open();
  SQLiteDataReader myReader = sqCommand.ExecuteReader(System.Data.CommandBehavior.Default);
  try
  {
    while (myReader.Read())
    {
      SQLiteBlob myBlob = myReader.GetSQLiteBlob(myReader.GetOrdinal("Picture"));
      if(!myBlob.IsNull)
      {
        string FN = myReader.GetString(myReader.GetOrdinal("PicName"));
        FileStream fs = new FileStream("D:\\Tmp\\"+FN+".bmp", FileMode.Create);
        BinaryWriter w = new BinaryWriter(fs);
        w.Write(myBlob.Value);
        w.Close();
        fs.Close();
        Console.WriteLine(FN+" downloaded.");
      }
    }
  }
  finally
  {
    myReader.Close();
    sqConnection.Close();
  }
}                                                                                                                   

public void UploadBlob(SQLiteConnection sqConnection)
{
  FileStream fs = new FileStream("D:\\Tmp\\_Water.bmp", FileMode.Open, FileAccess.Read);
  BinaryReader r = new BinaryReader(fs);
  SQLiteBlob myBlob = new SQLiteBlob(r.ReadBytes((int)fs.Length));
  SQLiteCommand sqCommand = new SQLiteCommand("INSERT INTO Pictures (ID, PicName, Picture) VALUES(1,'Water',:Pictures)", sqConnection);
  sqCommand.Parameters.Add("Pictures",myBlob);
  sqConnection.Open();
  try
  {
    Console.WriteLine(sqCommand.ExecuteNonQuery()+" rows affected.");
  }
  finally
  {
    sqConnection.Close();
    r.Close();
  }
}

Visual Basic

Public Sub DownloadBlob(ByVal sqConnection As SQLiteConnection)
  Dim sqCommand As New SQLiteCommand("SELECT * FROM Pictures", sqConnection)
  sqConnection.Open()
  Dim myReader As SQLiteDataReader = sqCommand.ExecuteReader(System.Data.CommandBehavior.Default)
  Try
    While myReader.Read()
      Dim myBlob As SQLiteBlob = myReader.GetSQLiteBlob(myReader.GetOrdinal("Picture"))
      If Not myBlob.IsNull Then
        Dim FN As String = myReader.GetString(myReader.GetOrdinal("PicName"))
        Dim fs As FileStream = New FileStream("D:\Tmp\" + FN + ".bmp", FileMode.Create)
        Dim w As BinaryWriter = New BinaryWriter(fs)
        w.Write(myBlob.Value)
        w.Close()
        fs.Close()
        Console.WriteLine(String.Concat(FN, " downloaded."))
      End If
    End While
  Finally
    myReader.Close()
    sqConnection.Close()
  End Try
End Sub

Public Sub UploadBlob(ByVal sqConnection As SQLiteConnection)
  Dim fs As FileStream = New FileStream("D:\Tmp\_Water.bmp", FileMode.Open, FileAccess.Read)
  Dim r As BinaryReader = New BinaryReader(fs)
  Dim myBlob As SQLiteBlob = New SQLiteBlob(r.ReadBytes(Convert.ToInt32(fs.Length)))
  Dim sqCommand As SQLiteCommand = New SQLiteCommand("INSERT INTO Pictures (ID, PicName, Picture) VALUES(2,'Water',:Pictures)", sqConnection)
  sqCommand.Parameters.Add("Pictures", myBlob)
  sqConnection.Open()
  Try
    Console.WriteLine(String.Concat(sqCommand.ExecuteNonQuery(), " rows affected."))
  Finally
    sqConnection.Close()
    r.Close()
  End Try
End Sub

Inheritance Hierarchy

System.Object
   System.MarshalByRefObject
      System.IO.Stream
         Devart.Data.SQLite.SQLiteBlob
            Devart.Data.SQLite.SQLiteText

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

SQLiteBlob Members
Devart.Data.SQLite Namespace

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