Here's the code in C#:

//Calculate the pages count
System.Drawing.Image img = Image.FromFile(@".\multi-page.tif");
Guid guid = img.FrameDimensionsList[0];
FrameDimension dimension = new FrameDimension(guid);
int totalFrame = img.GetFrameCount(dimension);

//Feed the pages to BarCodeReader one by one
Aspose.BarCode.BarCodeReader rd = new BarCodeReader();
for (int i = 0; i < totalFrame; i++)
{
   // Set the active page and feed it to the BarCodeReader
   img.SelectActiveFrame(dimension, i);
   rd.BarCodeImage = new Bitmap(img);
   BarCodeInfo[] infos = rd.Read();
   Console.Out.WriteLine("Page[" + i + "]");
   for (int j = 0; j < infos.Length; j++)
   {
      Console.Out.WriteLine("Found(" + j + ")" + infos[j].CodeText);
   }
}

And here's the code in VB.NET:

'Calculate the pages count
Dim img As Image = Image.FromFile("..\..\multi-datamatrix.tif")
Dim guid = img.FrameDimensionsList(0)
Dim dimension = New FrameDimension(guid)
Dim totalFrame = img.GetFrameCount(dimension)

'Feed the pages to BarCodeReader one by one
Dim rd = New Aspose.BarCode.BarCodeReader()

For i As Integer = 0 To totalFrame - 1
   ' Set the active page and feed it to the BarCodeReader
   img.SelectActiveFrame(dimension, i)
   rd.BarCodeImage = New System.Drawing.Bitmap(img)
   Dim infos As Aspose.BarCode.BarCodeInfo() = rd.Read()
   Console.Out.WriteLine("Page[" & i & "]")
   For j As Integer = 0 To infos.Length - 1
      Console.Out.WriteLine("Found(" & j & ")" & infos(j).CodeText)
   Next
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