# How to refence a custom udt property in an alarm property expression binding?

**URL:** <https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691>\
**Category:** Ignition\
**Tags:** ignition81\
**Created:** [July 8, 2022, 5:54pm UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691 "2022-07-08T17:54:09Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![mazeyrat](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mazeyrat/32/10955_2.png) [@mazeyrat](https://forum.inductiveautomation.com/u/mazeyrat)\
**Post date:** [July 8, 2022, 5:54pm UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691/1 "2022-07-08T17:54:09Z")

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**Ignition 8.1.18**

How to refence a custom udt property in an alarme expression binding

**alamConfig is a custom propertie of the UDT**  
The label propertie of an alarm has an expression binding which need to read this custom prop

Don’t work:

```auto
{[.]../alarmConfig}

{[.]../Customs.alarmConfig}

```

Seem to be impossible 😭 ?  
As a side note : I can’t use an UDT parameter instead of an UDT custom property because I need a **Document** property type.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/5/158e6f9e684c5546779b672b41c4037dce645dd6.png)

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<div class="post-metadata">

**Author:** ![mazeyrat](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mazeyrat/32/10955_2.png) [@mazeyrat](https://forum.inductiveautomation.com/u/mazeyrat)\
**Post date:** [July 13, 2022, 9:42am UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691/2 "2022-07-13T09:42:17Z")

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@ggross any idea how to access UDT custom property in expression for that use case ?

IMO, we definitely need somethink like the **parameters** synthax.

```auto
{[.]}../Parameters.xxxx

```

```auto
{[.]}../Customs.xxxx

```

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<div class="post-metadata">

**Author:** ![ggross](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ggross/32/12668_2.png) [@ggross](https://forum.inductiveautomation.com/u/ggross)\
**Post date:** [July 13, 2022, 3:21pm UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691/3 "2022-07-13T15:21:10Z")

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@mazeyrat, to be able to do this you would need to do something like:

`tag(concat('[.]../',{RootInstanceName},'.<Prop Name>'))`

We added the Pre-Defined Parameters `RootInstanceName` and `ParentInstanceName` in 8.1.13 for these types of relationships, so hopefully one of those can be used to get what you need.

The `Customs` and `Parameters` syntax is something I will discuss with the team. I can see how it could be useful.

Garth

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<div class="post-metadata">

**Author:** ![mazeyrat](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mazeyrat/32/10955_2.png) [@mazeyrat](https://forum.inductiveautomation.com/u/mazeyrat)\
**Post date:** [July 13, 2022, 3:37pm UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691/4 "2022-07-13T15:37:50Z")

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Thanks a lot !  
I missed the {RootInstanceName} and the support for “[.]…” in tag()  
I thinks that {[.]}…/Parameters.xxxx is already available ?

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<div class="post-metadata">

**Author:** ![ggross](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ggross/32/12668_2.png) [@ggross](https://forum.inductiveautomation.com/u/ggross)\
**Post date:** [July 13, 2022, 3:48pm UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691/5 "2022-07-13T15:48:48Z")

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Glad that worked.

Yes, the `{[.]}…/Parameters.xxxx` syntax is already there, my wording was just a bit off. It is considered by the system to be a folder which is why it works how it does. The custom props one might be a bit cumbersome to add because they aren’t separated out of the definition like parameters. We will discuss other options as well just to try and make it easier to find a solution to this type of situation as there is a clear problem that we should try and make better.

Garth

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<div class="post-metadata">

**Author:** ![mazeyrat](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mazeyrat/32/10955_2.png) [@mazeyrat](https://forum.inductiveautomation.com/u/mazeyrat)\
**Post date:** [July 13, 2022, 4:06pm UTC](https://forum.inductiveautomation.com/t/how-to-refence-a-custom-udt-property-in-an-alarm-property-expression-binding/61691/6 "2022-07-13T16:06:41Z")

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@ggross  
Another tricky item in expression synthax, is to obtain the folder name of a tag.  
I don’t find an elegant way to do this 🤔

As a side note:

```auto
system.tag.ReadBlocking(["path/to/Folder.name"])

```

give a folder name, but nothing in expression…

```auto
tag("[.]../name")

```

is not ok