public Band GetBandByType(
    Type type
)

Public Function GetBandByType(
    type As Type
) As Band

using DevExpress.XtraPrinting;
using DevExpress.XtraReports.UI;
// ...

public class XtraReport1 : DevExpress.XtraReports.UI.XtraReport {
// ...

    // ...
    // Generated code for the XtraReport1 class.
    // ...

    public void AddMarginBands() {

        // Check if the TopMargin band is already present in the report.
        if(Bands[BandKind.TopMargin] == null) {
            // Create a new TopMargin band and add it to the report.
            TopMarginBand tmBand = new TopMarginBand();
            Bands.Add(tmBand);

            // Create a label and set its text and width.
            XRLabel label = new XRLabel();
            label.Text = "TopMargin Band";
            label.Width = 200;

            // Add the label to the TopMargin band.
            tmBand.Controls.Add(label);
        }

        // Check if the BottomMargin band is already present in the report.
        if(Bands[BandKind.BottomMargin] == null) {
            // Create a new BottomMargin band and add it to the report.
            BottomMarginBand bmBand = new BottomMarginBand();
            Bands.Add(bmBand);

            // Create an XRPageInfo object and set its width and PageInfo option.
            XRPageInfo datePageInfo = new XRPageInfo();
            datePageInfo.Width = 200;
            datePageInfo.PageInfo = PageInfo.DateTime;

            // Add the page information control to the BottomMargin band.
            bmBand.Controls.Add(datePageInfo);
        }
    }

}

Imports DevExpress.XtraPrinting
Imports DevExpress.XtraReports.UI
' ...

Public Class XtraReport1
    Inherits DevExpress.XtraReports.UI.XtraReport
    ' ...

    ' ...
    ' Generated code for the XtraReport1 class.
    ' ...

    Public Sub AddMarginBands()

        ' Check if the TopMargin band is already present in the report.
        If Bands.GetBandByType(GetType(TopMarginBand)) Is Nothing Then
            ' Create a new TopMargin band and add it to the report.
            Dim tmBand As New TopMarginBand()
            Bands.Add(tmBand)

            ' Create a label and set its text and width.
            Dim label As New XRLabel()
            label.Text = "TopMargin Band"
            label.Width = 200

            ' Add the label to the TopMargin band.
            tmBand.Controls.Add(label)
        End If

        ' Check if the BottomMargin band is already present in the report.
        If Bands.GetBandByType(GetType(BottomMarginBand)) Is Nothing Then
            ' Create a new BottomMargin band and add it to the report.
            Dim bmBand As New BottomMarginBand()
            Bands.Add(bmBand)

            ' Create an XRPageInfo object and set its width and PageInfo option.
            Dim datePageInfo As New XRPageInfo()
            datePageInfo.Width = 200
            datePageInfo.PageInfo = PageInfo.DateTime

            ' Add the page information control to the BottomMargin band.
            bmBand.Controls.Add(datePageInfo)
        End If
    End Sub

End Class

XtraReport1 report = new XtraReport1();

private void btnPreview_Click(object sender, System.EventArgs e) {
    ReportPrintTool preview = new ReportPrintTool(report);
    preview.ShowPreview();
}

private void btnAddBands_Click(object sender, System.EventArgs e) {
    report.AddMarginBands();
}

Dim Report As New XtraReport1()

Private Sub BtnPreview_Click(sender As Object, e As System.EventArgs) _
Handles BtnPreview.Click
    Dim preview As New ReportPrintTool(report)
    preview.ShowPreview()
End Sub

Private Sub BtnAddBands_Click(sender As Object, e As System.EventArgs) _
Handles BtnAddBands.Click
    Report.AddMarginBands()
End Sub

DetailBand detailBand = report.Bands.GetBandByType(typeof(DetailBand)) as DetailBand;
PageHeaderBand pageHeaderBand =

Dim detailBand As DetailBand = TryCast(report.Bands.GetBandByType(GetType(DetailBand)), DetailBand)
Dim pageHeaderBand As PageHeaderBand = TryCast(report.Bands.GetBandByType(GetType(PageHeaderBand)), PageHeaderBand)