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

private void button1_Click(object sender, System.EventArgs e) {
    XtraReport1 report = new XtraReport1();

    // Create a barcode control.
    XRBarCode barcode = new XRBarCode();

    // Set the barcode's type to PostNet.
    barcode.Symbology = new PostNetGenerator();

    // Adjust the PostNet barcode's main properties.
    barcode.Text = "01234567"; 
    barcode.Width = 400;
    barcode.Height = 100;

    report.Detail.Controls.Add(barcode);
    report.ShowPreview();
}

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

Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles Button1.Click
    Dim report As New XtraReport1()

    ' Create a barcode control.
    Dim Barcode As New XRBarCode()

    ' Set the barcode's type to PostNet.
    Barcode.Symbology = New PostNetGenerator()

    ' Adjust the PostNet barcode's main properties.
    Barcode.Text = "01234567"
    Barcode.Width = 400
    Barcode.Height = 100

    report.Detail.Controls.Add(Barcode)
    report.ShowPreview()
End Sub