In this example, the WinForms TreeList control is bound to a collection of persistent objects. The example demonstrates how to add/create view properties (ViewProperty) on the fly using ConditionExpressionEditorForm and add coresponding calculated columns:
void OnShowExpressionEditorClick(object sender, EventArgs e) {
    using (ExpressionEditorForm editor = 
        new ConditionExpressionEditorForm(new TreeListDataColumnInfo(treeList1.Columns), null)) {
        if (editor.ShowDialog() == DialogResult.OK) {
            using (InputForm input = new InputForm()) {
                input.ShowDialog();
                xpView1.AddProperty(input.ColumnName, editor.Expression);
                treeList1.PopulateColumns();
            }
        }
    }
}- Run the project.
 - Click the Show Expression Editor button.
 - Create an expression (for example, "[Quantity] * [UnitPrice]").
 - Click OK.
 - Specify the name of a new calculated column (for example, "Total").
 - Click OK.
 
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