Merge and Split

protected void btnCreatePDF_Click(object sender, EventArgs e)
{
    string workingFolderPath = System.IO.Path.Combine(Server.MapPath("~"), "Files");

    string firstFilePath = System.IO.Path.Combine(workingFolderPath, "oss.pdf");
    string secondFilePath = System.IO.Path.Combine(workingFolderPath, "google.pdf");
    string mergedFilePath = System.IO.Path.Combine(workingFolderPath, "MergeFileResult.pdf");
    string extractedFilePath = System.IO.Path.Combine(workingFolderPath, "SplitFileResult.pdf");

    // merge files into disk file
    string[] filesToMerge = new string[2];
    filesToMerge[0] = firstFilePath;
    filesToMerge[1] = secondFilePath;
    // merge the two files into mergedFilePath on disk
    MergePdf.Merge(filesToMerge, mergedFilePath);

    // extract first page from the merged document and create a PDF file with it
    SplitPdf.ExtractPages(mergedFilePath, 0, 1, extractedFilePath);

    //merge streams
    System.IO.FileStream fs1 = new System.IO.FileStream(firstFilePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);
    System.IO.FileStream fs2 = new System.IO.FileStream(secondFilePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);

    System.IO.Stream[] streamsToMerge = new System.IO.Stream[2];
    streamsToMerge[0] = fs1;
    streamsToMerge[1] = fs2;

    // prepare Response
    Response.ClearContent();
    Response.Buffer = true;
    Response.AddHeader("content-disposition", "attachment; filename=MergeStreamsResult.pdf");
    Response.AddHeader("content-type", "application/pdf" );

    //Save the merge result directly on the Response stream to browser
    MergePdf.Merge(streamsToMerge, Response.OutputStream);

    //send buffered output to client browser
    Response.End();

    // close the source streams
    fs1.Close();
    fs2.Close();
}

Protected Sub btnCreatePDF_Click(sender As Object, e As EventArgs)
    Dim workingFolderPath As String = System.IO.Path.Combine(Server.MapPath("~"), "Files")

    Dim firstFilePath As String = System.IO.Path.Combine(workingFolderPath, "oss.pdf")
    Dim secondFilePath As String = System.IO.Path.Combine(workingFolderPath, "google.pdf")
    Dim mergedFilePath As String = System.IO.Path.Combine(workingFolderPath, "MergeFileResult.pdf")
    Dim extractedFilePath As String = System.IO.Path.Combine(workingFolderPath, "SplitFileResult.pdf")

    ' merge files into disk file
    Dim filesToMerge As String() = New String(1) {}
    filesToMerge(0) = firstFilePath
    filesToMerge(1) = secondFilePath
    ' merge the two files into mergedFilePath on disk
    MergePdf.Merge(filesToMerge, mergedFilePath)

    ' extract first page from the merged document and create a PDF file with it
    SplitPdf.ExtractPages(mergedFilePath, 0, 1, extractedFilePath)

    'merge streams
    Dim fs1 As New System.IO.FileStream(firstFilePath, System.IO.FileMode.Open, System.IO.FileAccess.Read)
    Dim fs2 As New System.IO.FileStream(secondFilePath, System.IO.FileMode.Open, System.IO.FileAccess.Read)

    Dim streamsToMerge As System.IO.Stream() = New System.IO.Stream(1) {}
    streamsToMerge(0) = fs1
    streamsToMerge(1) = fs2

    ' prepare Response
    Response.ClearContent()
    Response.Buffer = True
    Response.AddHeader("content-disposition", "attachment; filename=MergeStreamsResult.pdf")
    Response.AddHeader("content-type", "application/pdf")

    'Save the merge result directly on the Response stream to browser
    MergePdf.Merge(streamsToMerge, Response.OutputStream)

    'send buffered output to client browser
    Response.[End]()

    ' close the source streams
    fs1.Close()
    fs2.Close()
End Sub