PgSqlLargeObject Class

In This Topic

Represents a PostgreSQL large object.

Syntax

Visual Basic
C#

'Declaration
 
Public Class PgSqlLargeObject 
   Inherits System.IO.Stream
   Implements System.Data.SqlTypes.INullable, System.IDisposable

public class PgSqlLargeObject : System.IO.Stream, System.Data.SqlTypes.INullable, System.IDisposable

Remarks

The PgSqlLargeObject class is used to work with PostgreSQL large objects. An instance of PgSqlLargeObject holds an OID of large object and can be used for operations with this large object.

Note: all operations with large objects require an active transaction.

Example

The following example shows how to create and manage large objects with PgSqlLargeObject.

csharp

public static void Main(string[] args) {

        PgSqlConnection connection = new PgSqlConnection("user id=postgres;password=postgres;port=5432;host=localhost;");
        connection.Open();

        int oid = CreateLargeObject(connection);
        WriteToLargeObject(connection, oid);
        ReadFromLargeObject(connection, oid);

        Console.ReadLine();
}

public static int CreateLargeObject(PgSqlConnection connection) {

        PgSqlLargeObject lo = new PgSqlLargeObject(connection);
        // Create a new large object in the database.
        lo.Create();
        Console.WriteLine("Created new large object with OID = {0}", lo.Oid);

        return lo.Oid;
}

public static void WriteToLargeObject(PgSqlConnection connection, int oid) {
        // All operations with large objects require an active transaction.
        connection.BeginTransaction();
        string str = "Hello, world!";
        PgSqlLargeObject lo = new PgSqlLargeObject(connection, oid);
        lo.Open();

        if (lo.CanWrite) {
                byte[] buffer = Encoding.UTF8.GetBytes(str);
                lo.Write(buffer, 0, buffer.Length);
        }
        lo.Close();

        Console.WriteLine("Written to the large object : {0}", str);
        connection.Commit();
}

public static void ReadFromLargeObject(PgSqlConnection connection, int oid) {
        // All operations with large objects require an active transaction.
        connection.BeginTransaction();
        string str = string.Empty;
        PgSqlLargeObject lo = new PgSqlLargeObject(connection, oid);
        lo.Open();

        if (lo.CanWrite) {
                byte[] buffer = new byte[lo.Length];
                lo.Read(buffer, 0, buffer.Length);
                str = Encoding.UTF8.GetString(buffer);
        }
        lo.Close();

        Console.WriteLine("Read from the large object : {0}", str);
        connection.Commit();
}

Visual Basic

Public Sub Main()
        Dim connection As New PgSqlConnection("user id=postgres;password=postgres;port=5432;host=localhost;")
        connection.Open()

        Dim oid As Integer = CreateLargeObject(connection)
        WriteToLargeObject(connection, oid)
        ReadFromLargeObject(connection, oid)
        Console.ReadLine()
End Sub

Public Function CreateLargeObject(ByVal connection As PgSqlConnection) As Integer
        Dim lo As New PgSqlLargeObject(connection)
        ' Create a new large object in the database.
        lo.Create()
        Console.WriteLine("Created new large object with OID = {0}", lo.Oid)
        Return lo.Oid
End Function

Public Sub WriteToLargeObject(ByVal connection As PgSqlConnection, ByVal oid As Integer)
        ' All operations with large objects require an active transaction.
        connection.BeginTransaction()
        Dim str As String = "Hello, world!"
        Dim lo As New PgSqlLargeObject(connection, oid)
        lo.Open()
        If lo.CanWrite Then
                Dim buffer As Byte() = Encoding.UTF8.GetBytes(str)
                lo.Write(buffer, 0, buffer.Length)
        End If
        lo.Close()
        Console.WriteLine("Written to the large object : {0}", str)
        connection.Commit()
End Sub

Public Sub ReadFromLargeObject(ByVal connection As PgSqlConnection, ByVal oid As Integer)
        ' All operations with large objects require an active transaction.
        connection.BeginTransaction()
        Dim str As String = String.Empty
        Dim lo As New PgSqlLargeObject(connection, oid)
        lo.Open()
        If lo.CanWrite Then
                Dim buffer As Byte() = New Byte(lo.Length - 1) {}
                lo.Read(buffer, 0, buffer.Length)
                str = Encoding.UTF8.GetString(buffer)
        End If
        lo.Close()
        Console.WriteLine("Read from the large object : {0}", str)
        connection.Commit()
End Sub

Inheritance Hierarchy

System.Object
   System.MarshalByRefObject
      System.IO.Stream
         Devart.Data.PostgreSql.PgSqlLargeObject

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

PgSqlLargeObject Members
Devart.Data.PostgreSql Namespace

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