> For the complete documentation index, see [llms.txt](https://docs.wem.io/platform/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.wem.io/platform/tutorials/building-widgets/wemscript/8-types/3-conceptset.md).

# 3. ConceptSet

A `conceptset` type holds a set of items of type `concept`. This `conceptset` has no predefined range and accepts any `concept`, which distinguishes it from a concept data field that does have a range.

```wemscript
<?
    var @cs: conceptset

    /* Assign the concept set with a single concept from @ConceptProperty1 */
    @cs := @ConceptProperty1
    
    /* Loop through the range of the concept set data field */
    loop range of @ConceptSetProperty
        /* Add the current concept from the range to the concept set @cs */
        @cs := @cs + concept
    end

    /* Remove @ConceptProperty2 from the concept set @cs */
    @cs := @cs - @ConceptProperty2

    /* Loop through the concepts included in the concept set of @ConceptSetProperty */
    loop @ConceptSetProperty
        /* ... */
    end
?>
```

#### Checkbox List Example

```html
<? register input @ConceptSetProperty ?>
<? var @id := OutputId(@ConceptSetProperty) ?>
<? loop range of @ConceptSetProperty ?>
	<label>
		<input 
			type="checkbox" 
			name="<?attr @id ?>" <? if @ConceptSetProperty contains concept ?>checked<? end ?>
			value="<?attr ConceptId(concept) ?>"
		>
		<?= concept ?>
	</label>
<? end ?>
```

In this example, we `register input` for our `@ConceptSetProperty`, and we store the output ID in a variable called `@id`. This is important because all checkboxes must share the same name according to HTML specifications. Next, we `loop` through the `range of @ConceptSetProperty` to generate the checkboxes. We set the name to `@id`, the value to `ConceptId(concept)`, and check if `@ConceptSetProperty contains concept`. If it does, we add the "checked" attribute to the checkbox. After rendering the checkbox input, we display the name of the concept using `<?= concept ?>`.

In the background, during a postback, we send back a list of IDs that will update the data model bound to `@ConceptSetProperty`.

#### Textbox Example

The following example demonstrates a less user-friendly UX for updating a concept set. However, it illustrates the concept of updating a concept data model with a postback using a single input field—in this case, a text field.

```wemscript
<? 
	register input @ConceptSetProperty
	
	var @ids: text
	
	loop range of @ConceptSetProperty 
?>
	<div>
		<? 
			var @included := @ConceptSetProperty contains concept
			
			if @included
				@ids := @ids + (if Length(@ids) <> 0 then "," else "") + ConceptId(concept)
			end
		?>
		<?= ConceptId(concept) ?>: <?= concept ?> <? if @included ?>(included)<? end ?>
	</div>
<? end ?>
<div>
    <input type="text" name="<?attr OutputId(@ConceptSetProperty) ?>" value="<?attr @ids ?>">
</div>
```

This widget renders all the concepts along with their concept IDs from the range of `@ConceptSetProperty`. When `@ConceptSetProperty contains concept`, that concept will be included in the value of the text field. The result will be a comma-separated list of IDs, e.g., `1,23,400`. To update the concept set, you simply modify the text value, which holds the IDs that are part of this concept set. Note that the format is very strict; for instance, the value `3,70,` with an additional trailing comma at the end is not accepted by the WEM runtime and will result in an empty concept set.


---

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