# Ignition 7.9 Expression

**URL:** <https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440>\
**Category:** Ignition\
**Created:** [May 11, 2022, 2:27am UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440 "2022-05-11T02:27:29Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![xtristan](https://avatars.discourse-cdn.com/v4/letter/x/ba8739/32.png) [@xtristan](https://forum.inductiveautomation.com/u/xtristan)\
**Post date:** [May 11, 2022, 2:27am UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/1 "2022-05-11T02:27:29Z")

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Is anyone familiar with the use of ‘::’ in an expression binding?

I am troubleshooting a screen and see a reference like {Page.PropertyThatDoesn’tExist::PropertyThatDoesn’tExist.Property That Doesn’t Exist} I don’t see how the property binding is related to the page and believe the page currently doesn’t work but have never seen ‘::’ used before and am looking for any info that can point me to its use

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**Author:** ![xtristan](https://avatars.discourse-cdn.com/v4/letter/x/ba8739/32.png) [@xtristan](https://forum.inductiveautomation.com/u/xtristan)\
**Post date:** [May 11, 2022, 2:30am UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/2 "2022-05-11T02:30:08Z")

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Template not page

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [May 11, 2022, 11:18am UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/3 "2022-05-11T11:18:19Z")

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Doesn’t seem to be valid for Vision expressions at all.

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**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [May 11, 2022, 3:29pm UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/4 "2022-05-11T15:29:30Z")

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`{Root Container.a::Tag 1}`  
Is a property reference to member `Tag 1` of the custom data type property binding `a` on the root container.

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<div class="post-metadata">

**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [May 11, 2022, 3:51pm UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/5 "2022-05-11T15:51:41Z")

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Ah, sorry. I don’t _ **ever** _ use UDT properties.

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**Author:** ![lrose](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/lrose/32/62724_2.png) [@lrose](https://forum.inductiveautomation.com/u/lrose)\
**Post date:** [May 11, 2022, 3:56pm UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/6 "2022-05-11T15:56:21Z")

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Is that referenced anywhere?

It’s definately not here:  
[https://docs.inductiveautomation.com/display/DOC79/Expression+Overview+and+Syntax](https://docs.inductiveautomation.com/display/DOC79/Expression+Overview+and+Syntax)

It’s not in the 8.1 version of the same page either.

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<div class="post-metadata">

**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [May 11, 2022, 5:08pm UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/7 "2022-05-11T17:08:11Z")

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Probably not.  
Everything inside the curly braces is passed to the local expression’s contextual “property resolver”, so despite common syntax choices inside the curly braces, technically e.g. alarm pipelines vs tags vs Perspective vs Vision each have their “own” implementation of property lookup. So if it were to go anywhere, it would be a Vision specific expression page, not on the general syntax overview.

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<div class="post-metadata">

**Author:** ![xtristan](https://avatars.discourse-cdn.com/v4/letter/x/ba8739/32.png) [@xtristan](https://forum.inductiveautomation.com/u/xtristan)\
**Post date:** [May 11, 2022, 5:50pm UTC](https://forum.inductiveautomation.com/t/ignition-7-9-expression/59440/8 "2022-05-11T17:50:07Z")

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Thank you I think this is it, probably just a copy and paste template