CanSeek Property (PgSqlBlob)

In This Topic

Gets a value indicating whether forward and backward seek operations can be performed.

Syntax

Visual Basic
C#

'Declaration
 
Public Overrides ReadOnly Property CanSeek As Boolean

public override bool CanSeek {get;}

Property Value

true if the PgSqlBlob stream supports seeking; false if a PgSqlBlob is closed, disposed, or Null.

Remarks

Use this property to find out if a PgSqlBlob supports Seek operation. PgSqlBlob does not support seeking if it has Null value as well as if it has been disposed or closed.

Example

csharp

void ReverseBlob()
{
  byte[] byteArray = { (byte)'A', (byte)'B', (byte)'C' };
  PgSqlBlob blobFrom = new PgSqlBlob(byteArray);
  //blobFrom.ToString() = "ABC"

  PgSqlBlob blobTo = new PgSqlBlob();
  ........
  //reverse PgSqlBlob
  if (blobFrom.CanSeek && blobFrom.CanRead && blobTo.CanWrite)
    for (blobFrom.Seek(-1, System.IO.SeekOrigin.End); ;blobFrom.Position -= 2)
    {
      blobTo.WriteByte((byte)blobFrom.ReadByte());
      if (blobFrom.Position == 1) break;
    }
  //blobTo.ToString() = "CBA";
}

Visual Basic

Private Sub ReverseBlob()
  Dim byteArray As Byte() = New Byte() {AscW("A"c), AscW("B"c), AscW("C"c)}
  Dim blobFrom As New PgSqlBlob(byteArray)
  ' blobFrom.ToString() = "ABC"

  Dim blobTo As New PgSqlBlob
  ......
  ' reverse PgSqlBlob
  If ((blobFrom.CanSeek AndAlso blobFrom.CanRead) AndAlso blobTo.CanWrite) Then
    blobFrom.Seek(CLng(-1), System.IO.SeekOrigin.End)
    Do While True
      blobTo.WriteByte(CByte(blobFrom.ReadByte))
      If (blobFrom.Position = 1) Then
        Return
      End If
      blobFrom.Position = blobFrom.Position - 2
    Loop
  End If
  ' blobTo.ToString() = "CBA";
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

PgSqlBlob Class
PgSqlBlob Members

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