Preview Sections

• Nov 13, 2018
• 2 minutes to read

Preview sections are non-editable regions that allow nodes to display large memo text or custom data. They are displayed under nodes’ data cells across all columns.

Contents - Displaying Data from a Single Field

To display preview sections, do the following:

1. Set the TreeListOptionsView.ShowPreview property to true.
2. Set the TreeList.PreviewFieldName property to a field that automatically provides data for preview sections.

Custom Contents

Set the TreeListOptionsView.ShowPreview property to true, and then handle one of the following events to provide custom contents for preview sections:

• TreeList.GetPreviewText - Allows you to provide custom text for preview sections.
• TreeList.CustomDrawNodePreview - Allows you to manually paint text and graphics elements in preview sections.

Example

The sample code below handles the TreeList.GetPreviewText event. This is used to display values of the Location and Phone fields within preview sections of nodes.

The image illustrates the result of sample code execution.

C#

using DevExpress.XtraTreeList;

private void treeList1_GetPreviewText(object sender, GetPreviewTextEventArgs e) {
   e.PreviewText = "Office Location: " + e.Node["Location"].ToString() + "; Phone: " + 
     e.Node["Phone"].ToString();
}

VB.NET

Private Sub TreeList1_GetPreviewText(ByVal sender As Object, _
ByVal e As GetPreviewTextEventArgs) Handles TreeList1.GetPreviewText
   e.PreviewText = "Office Location: " + e.Node("Location") + "; Phone: " + e.Node("Phone")
End Sub

Height

Use the following members to specify preview section height:

• TreeList.PreviewLineCount - Gets or sets the number of text lines in preview sections.

  This property is set to 2 in the following image:

  

• TreeListOptionsView.AutoCalcPreviewLineCount - Gets or sets whether the number of text lines in preview sections is calculated automatically depending on their contents.
• TreeList.MeasurePreviewHeight - This event allows you to specify individual preview sections’ height in pixels.

Appearance

• TreeListAppearanceCollection.Preview - Gets the appearance settings used to paint preview sections.
• TreeList.CustomDrawNodePreview - Allows you to customize the appearance settings while custom painting preview sections.

Printing API

• TreeListOptionsPrint.PrintPreview - Gets or sets whether preview sections are printed.
• TreeList.GetPrintPreviewText - Enables you to display custom text in preview sections when the control is printed.
• TreeListPrintAppearanceCollection.Preview - Gets the appearance settings used to paint the preview sections when the Tree List is printed.