# Ignition 7 String Bind to UDT Parameter

**URL:** <https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236>\
**Category:** Ignition\
**Tags:** ignition77, vision\
**Created:** [May 10, 2024, 3:17pm UTC](https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236 "2024-05-10T15:17:14Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\
**Post date:** [May 10, 2024, 3:17pm UTC](https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236/1 "2024-05-10T15:17:14Z")

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I'm trying to bind a string member directly to a string parameter for a UDT but I'm getting an evaluation error and I get "null".

The parameter's type is a string, the member is a string expression tag and only references the parameter.

If I do it with an int parameter and an int expression tag it works. I've also tried `toStr()` in the expression and that doesn't change anything.

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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 10, 2024, 10:19pm UTC](https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236/2 "2024-05-10T22:19:51Z")

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Prior to v8, such string parameters needed to be quoted, as the parameters are not true expression variables.

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**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\
**Post date:** [May 13, 2024, 1:14pm UTC](https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236/3 "2024-05-13T13:14:04Z")

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If I'm using the same string parameter in an expression for OPC path, are the quotes going to mess that up then?

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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 13, 2024, 1:17pm UTC](https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236/4 "2024-05-13T13:17:25Z")

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In Ignition 7.x, UDT parameters are not implemented with the expression language, like is done n v8+. In v7, UDT parameters are injected with string interpolation, independent of any other operations. If, after injection, they need to be used as string constants in an expression or script, they need to be quoted.

You will need to experiment. I don't imagine many people think about the intricacies of obsolete software like this.

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**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\
**Post date:** [May 14, 2024, 7:15pm UTC](https://forum.inductiveautomation.com/t/ignition-7-string-bind-to-udt-parameter/90236/5 "2024-05-14T19:15:34Z")

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This information is not particularly useful, since 7.7 is obsolete, but I'll include it anyway.

I tested it. Using quotes, the string tag expression binding directly to the UDT works, but it breaks the OPC path and the quotes are shown when it's used in alarm configuration.

The workaround is to use 2 string parameters. One string that's used in OPC path and alarm config, one that binds directly to the string expression tag.