---
title: Cascading dropdown data bind
summary: Binds Column1/Column2 value lists from data sources and registers the client-side cascading filter script.
status: draft
owner: SAIF Documentation Team
last_reviewed: 2026-08-17
library: SAIF.Presentation.Web.Controls.Infragistics103
reference_type: package
operation_id: OP-DROPDOWN-DATABIND
trigger: Explicit DataBind() call from a consuming page/control, or ASP.NET data-binding cascade
---

# Cascading dropdown data bind

This operation runs when a consuming page or control calls `DataBind()` on a `clsDropDownController` instance (typically during grid setup), binding two `UltraGridColumn` value lists and registering the generated client-side cascading-filter script.

| Field | Value |
| --- | --- |
| **Operation ID** | OP-DROPDOWN-DATABIND |
| **Trigger** | Explicit call from a consuming page/control, or ASP.NET data-binding cascade if the control is added to a naming container that calls `DataBind()` |
| **Inputs** | `Column1`, `Column2` (grid columns), `List1`, `List2` (data sources), `List1Code`/`List1Display`/`List2Code`/`List2Display`/`List2Key` (property-name selectors) |
| **Outputs** | Populated `Column1.ValueList`/`Column2.ValueList`, registered client script block `"DD"`, populated `l1`/`l2` collections |
| **Primary components** | `clsDropDownController.DataBind` |
| **Entry point** | SAIF.Presentation.Web.Controls.Infragistics103\clsDropDownController.vb |

## Steps

1. Call `MyBase.DataBind()`.
2. Bind `Column1.ValueList` from `List1` using `List1Display`/`List1Code` as display/value members; bind `Column2.ValueList` from `List2` using `List2Display`/`List2Code`.
3. Set `Column1.Band.Grid.DisplayLayout.ClientSideEvents.BeforeEnterEditModeHandler = "BeforeEdit" & Column2.Key` — wires a client-side hook so entering edit mode on Column2 triggers the generated JS filter function ([BR-5](../business-rules.md#br-5-cascading-dropdown-filters-column2-options-by-column1-key)).
4. Iterate `List1`: for each item, use `TypeDescriptor.GetProperties` reflection to find the property matching `List1Code` (→ `ListItem.id`) and `List1Display` (→ `ListItem.desc`); only properties whose type has a `TypeConverter` convertible to `String` are read. Append each `ListItem` to `l1`.
   - If no converter is found (`converter Is Nothing`): the value is silently skipped (left blank on the `ListItem`) — no exception is raised.
5. Iterate `List2` similarly, additionally capturing `List2Key` (→ `ListItem.key`), appending to `l2`.
6. Call `GenerateJavaScript()` twice — once discarded, once passed to `Page.ClientScript.RegisterClientScriptBlock(Me.GetType, "DD", GenerateJavaScript())` to emit the generated client-side filter script (function name `BeforeEdit` + `Column2.Key`) into the page. See [Cascading dropdown JavaScript generation](cascading-dropdown-javascript-generation.md) for the full generated-script content and behavior.
   - The first, discarded call is redundant/dead computation rather than commented-out code — both calls execute live code, so both are reported; the first result is simply unused.

> **Origin**: Step 6 delegates the JavaScript-generation logic to `GenerateJavaScript()`, documented in full as [Cascading dropdown JavaScript generation](cascading-dropdown-javascript-generation.md) (same class, same library).

## Process flow

The following diagram visualizes this operation's control flow.

```mermaid
flowchart TD
	Start([DataBind called]) --> Base[Call MyBase.DataBind]
	Base --> BindCols[Bind Column1/Column2 ValueList from List1/List2]
	BindCols --> WireEvent[Set BeforeEnterEditModeHandler on Column1's grid]
	WireEvent --> Loop1[Iterate List1 via reflection into l1 ListItems]
	Loop1 --> Loop2[Iterate List2 via reflection into l2 ListItems]
	Loop2 --> Gen[Call GenerateJavaScript twice]
	Gen --> Register[RegisterClientScriptBlock 'DD']
	Register --> EndOk([DataBind complete])
```

## Failure and edge-case behavior
- No `TypeConverter` found for a reflected property: the corresponding `ListItem` field (`id`/`desc`/`key`) is silently left blank; no exception is raised.

## Related documentation
- [Operations and processes](../operations-processes.md)
- [Business rules](../business-rules.md)

## Sources
- SAIF.Presentation.Web.Controls.Infragistics103\clsDropDownController.vb